During this period, an organism emerges from a fertilized egg, possessing primitive structures of various systems and organs. Intrauterine development divided into pre-fetal and fetal stages. The boundary between them is the end of the second month of the embryo’s life, when it turns into a fetus.
The beginning of time
Fetal development begins not from the embryonic period, but even earlier, because the embryo develops from a fertilized egg, and fertilization of the egg is preceded by the long development of germ cells.
The pre-embryonic period includes the maturation of germ cells and fertilization.
If in the testes of men constant renewal of germ cells occurs on average every 2 months, then in the ovaries of women there is no renewal. After the birth of a girl, there are only about 400 thousand cells in her ovaries - the precursors of eggs, which are given to her for life. In each menstrual cycle, one, or less often two, eggs are released from the ovary. This process is called ovulation. After leaving the ovary, the egg enters the fallopian tube, where fertilization occurs - the fusion of the female and male reproductive cells.
This fusion leads to the formation of a qualitatively new cell - a zygote. The zygote moves through the fallopian tube into the uterine cavity (this period lasts 7-8 days). When the zygote reaches the uterus, implantation begins - the implantation of the zygote into the wall of the uterus. The implantation process lasts 3 days.
In the prefetal period, intensive anatomical formation of the rudiments of organs that arose during the formation of the embryo occurs, and new anlages arise: the stomach and other parts of the digestive tract are distinguished, the intestinal anlage is divided into sections, the muscles are separated, and the skeleton is formed. In the second half of the prefetal period, the facial parts and neck are formed, the circulatory system and sensory organs develop, the structure of the brain becomes more complex, and large digestive glands are secreted - the liver and pancreas. By the end of the second month, the rudiments of all organs are formed and occupy their permanent position.
During the fetal period, growth and functional maturation of fetal organs and tissues occur, i.e. starting from this period, the fetal organs acquire the ability to function.
Second month. In the embryo (its length is 4 - 5 mm), the anlage of the limbs becomes noticeable. By the end of the second month, the length of the embryo increases from 5 mm (at the 5th week) to 25 - 30 mm. The hands and feet have fingers that are already capable of movement; but these movements are not yet felt by the mother. The rather long tail gradually turns into a small tubercle. The neck is being formed. The brain stops showing through the skin. The rudiments of the sensory organs are formed from the protrusions and depressions of the brain, while the eyes are already almost completely formed. The size of the head is very large (it is about half the length of the entire embryo). Constant relationships are established between the main structures of the face, with the exception of the ears, which are located very low. The fetal body begins to function: the brain sends impulses that coordinate the functions of other organs, the heart beats, the stomach secretes gastric juice, the liver produces blood cells. The rapid growth of the intestine, which began in the 6-7th week, leads to the fact that some of the intestinal loops no longer fit in the small abdominal cavity of the embryo and extend beyond its limits. A so-called physiological umbilical hernia occurs, which reaches full development by the end of the second month, and completely disappears by the 10th week. At the end of the second month (8 weeks), the fetal body is formed, the rudiments of the limbs are present, the rudiments of the eyes, nose, and mouth are visible on the head, and the formation of the genital organs begins.
Third month. The total length of the fetus, including legs, is 7 cm, weight - 20 g. During the third month, the fetus grows rapidly and almost doubles its length. The head still remains relatively large and by the end of the month is about l/3 of the parietal-coccygeal length. The facial part is very small compared to the brain part of the skull. There is rapid growth of the eyelids, the edges of which fuse together in the 9th-10th week of embryonic development. The eyes open only in the seventh month of pregnancy. The first rudiments of hair appear (on the eyebrows, upper and lower lips, on the forehead). The limbs move, fingers and toes are visible, and the first points of ossification appear in the cartilaginous rudiment of the skeleton. Nail rudiments form on the fingers and toes. The fetus already knows how to grimace. Special studies have found that fetal facial expressions reflect changes in his mother's face when laughing or crying. The hands grow so much that the fetus can touch its head with its fingers and can clench its fists. At the beginning of the third month, the urogenital and anal openings appear. Based on the structure of the external genitalia, the sex of the fetus can be determined. By the end of the third month, the skin begins to lose the transparency characteristic of it in the first two months of intrauterine life.
Fourth month. The total length of the fetus, including legs, is 15-18 cm, weight - 120 g. The head begins to lag somewhat behind in growth. Vellus hair appears on the body. The arms and legs are approximately the same length. The face is formed, the skull ossifies, the formation of the muscular system basically ends, the movements of the limbs become more active, but are not yet perceived by the mother, the sex of the fetus is clearly distinguished. The fetus moves a lot and can suck its own finger. The skin has several layers. The functions of various body systems become more complex. Using electron microscopy, it was found that the structure of nerve cells in the brain of a fetus of this age is almost the same as in newborns. It is already well possible to listen through the abdominal wall of a pregnant woman to the fetal heartbeat, the frequency of which reaches 120-150 beats per minute. By the end of the fourth month, an increase in the pregnant woman’s abdomen becomes noticeable.
Fifth month.(The total length of the fetus, including legs, is 22 cm, weight - 300 g). The body grows more rapidly, and by the end of the fifth month of intrauterine development the head is no more than l/3 of the total body length. The skin is dark red in color. A subcutaneous fat layer begins to form. The skin is covered with vellus hair. The sebaceous glands begin to secrete a fatty substance, which mixes with the scales of the epidermis and forms a cheese-like lubricant. This lubricant protects the fetus from constant exposure to amniotic fluid, and then facilitates its passage through the birth canal. Meconium forms in the intestines. The lower limbs are noticeably lengthened. The fetus can be born alive and makes breathing movements, but at this stage of pregnancy it is usually not viable.
He is no longer so free in the amniotic sac, and his motor activity increases. In the 3rd week of the fifth month, a woman who is pregnant for the first time begins to feel these movements. Repeatedly pregnant women notice them 10 days earlier. At first, the movements are very weak - women may confuse them with intestinal contractions. Later, the movements of the fetus become more and more intense, and they can no longer be confused with anything. The mother's first registration of fetal movements is an important sign that allows one to calculate the date of the upcoming birth.
Sixth month. The total length of the fetus, including legs, is 30 cm, weight - 800 g. The skin of the fetus becomes wrinkled, apparently due to a discrepancy between the growth rate of the fetus itself and its skin. Eyebrows and eyelashes become noticeable. Skin patterns form on the fingertips. Each of them has their own design - unique and inimitable. During this period, the formation of cells in the cerebral cortex is largely completed. Their loss under the influence of any damaging factors is not compensated. A person lives all his life with the number of cells that have formed the cerebral cortex by that time. Fetal movements become more differentiated. By observing the fetus using ultrasound, German scientists have learned to determine by the position of the hands whether the fetus is in a state of wakefulness or sleep. The organs and systems of the fetus continue to develop, master new functions, but are not yet perfect enough and are not able to support the life of the fetus outside the womb.
Seventh and eighth months. The total length of the fetus, including legs, is 35-40 cm, weight - 1200-1700 g. The subcutaneous fat layer increases, and the skin becomes denser and smoother. In the seventh month of pregnancy, the fetus's eyelids open. He can open and close his eyes. By this time, his entire body is covered with delicate vellus hairs. In recent weeks, weight gain is mainly due to subcutaneous fat, which ensures the maintenance of a stable body temperature after childbirth. All the most important systems of the body are sufficiently developed and can, although with great difficulty, with special care, support the life of the baby outside the mother’s body.
At around seven and a half months, the fetus can be born and survive. Babies born during the third trimester (from the seventh month until the end of pregnancy) are usually able to survive, although as the due date approaches, both the chance of survival and the ease of transition to independent existence increase significantly. Towards the end of pregnancy, antibodies from the mother cross the placenta to the fetus, creating short-term resistance to diseases to which you are immune. Premature babies receive less of this protection than full-term babies and are therefore more susceptible to infections.
Ninth month. The total length of the fetus, including legs, is 45 cm. Due to the strong deposition of fat in the subcutaneous fatty tissue, the shape of its body becomes more rounded. The fingernails reach to the fingertips. The hair on the head becomes thicker and longer. The fetus born at this time is viable, screams loudly, opens its eyes, and the sucking reflex is expressed.
In the eighth - tenth months the growth rate of the fetus decreases. He is already so big that he feels cramped in the amniotic sac. In this situation, the most advantageous position, providing maximum mobility in the funnel-shaped uterus, is the head down position. A normally developing fetus accepts it. Head presentation is most favorable during obstetrics. By the end of the ninth month, the fetal body is so perfect that it is finally ready for extrauterine life. Delicate hairs remain only on the forearms. Their severity and distribution throughout the body may indirectly indicate insufficient fetal maturity.
Tenth month. The total length of the fetus, including legs, is 50 cm, weight - 3000 g. By the end of the tenth month of pregnancy (38-40 weeks), signs of prematurity disappear, and the fetus is born mature. A discrepancy between term and fetal maturity is relatively rarely observed. Under unfavorable developmental conditions (maternal illness, insufficient or unhealthy nutrition, etc.), a full-term baby may have signs of immaturity. Sometimes the opposite phenomenon is observed: the child is born a little ahead of schedule, but mature.
IN last month there is a faster growth of the lower extremities, and the difference in length compared to the upper extremities is smoothed out. However, it is only after birth that the legs become longer than the arms.
Let us remind you that the correct intrauterine development of a baby largely depends on its mother. During the examination, follow all the recommendations and the doctor’s appointment - and the child will be born healthy.
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The birth of a new life is the most beautiful secret of nature. What could be more mysterious than the development of a child in the womb? The formation of a little person from a fertilized egg goes through a rather complicated path. Expectant mothers will be very interested to know how the child’s intrauterine development occurs week by week.
Initial development of pregnancy
Pregnancy lasts 40 weeks or 10 obstetric months. The term “obstetric month” implies 28 calendar days. But the first day is considered the beginning of pregnancy itself. menstrual cycle. Thus, according to medical calculations, pregnancy lasts not 40, but 38 weeks.
So, fertilization occurred: the sperm penetrated the egg and formed a single cell with two nuclei. These nuclei, moving towards each other, form a zygote. A zygote is a one-celled embryo. This fact is the beginning of the development of a new life.
The zygote lives for 30 hours, after which its first division occurs. In subsequent days, cell division is repeated. On the fourth day of life, the embryo consists of 8-12 cells. By this time, this small lump reaches the uterine cavity, where the process of cell division intensively increases.
By the seventh day, the embryo already consists of hundreds of cells. On the eighth day, the embryo attaches to the wall of the uterus, where its walls have acquired a loose and thickened structure. The implantation process takes about 40 hours.
On the 14th day of the embryo's life, its back part thickens, preparing for the formation of the main organs.
Already in the second week after fertilization, pregnancy can be determined using tests. Already on the 3rd day of its life, a small embryo begins to produce a hormone - gonadoprin. All pregnancy tests are sensitive to this hormone.
At the end of the 4th week, a woman notices the absence of menstruation. The first symptoms of pregnancy will appear: nausea, dizziness, drowsiness.
During this period, the embryo is already called an embryo, the size of which is about 1 mm.
The development of a child in the womb can be divided into three main periods:
- Blastogenesis - the first 15 days.
- Organogenesis is the development of the embryo from 15 days to 10 weeks of pregnancy.
- The fetal period is the development of the fetus in the womb.
If we divide the entire pregnancy into 3 equal periods, we get the following time periods: first, second and third trimesters. Each trimester lasts 3 months.
If a woman is not yet aware of her “interesting situation” and continues to lead an inappropriate lifestyle, then the embryo will most likely die at the blastogenesis stage. If the mother's destructive lifestyle does not change during the first 12 weeks, there is a high probability of miscarriage.
Embryonic development of a child in the womb
Embryo development is a key moment of pregnancy, since during this period all vital organs are formed, which will affect the baby’s health in the future.
Mommy should never be nervous: only peace and positive emotions!
By the end of week 5, the embryo consists of three cell layers: ectoderm, endoderm and mesoderm. Ectoderm is the basis of the nervous system, hair and skin. The endoderm will develop in the future into the gastrointestinal tract. The mesoderm will turn into skeletal and muscle tissue, and will also form the basis of the circulatory, excretory and reproductive systems.
At week 5, a kind of heart tube is formed. We can assume that from this moment the embryo’s “heart” begins to beat. 
A groove is formed on the back of the embryo, which is the basis of the spinal cord and the entire nervous system. It is very important for the expectant mother to take enough folic acid during this period. This substance promotes the full formation of the nervous system of the unborn child.
At week 6, the embryo takes on a C-shape. During this period, the formation of the primary intestine, skeletal cartilage, liver, kidneys, and thyroid gland occurs. The small embryo reaches 4 mm.
At the 7th week of pregnancy, women experience toxicosis. This period is characterized by intensive development of the brain. The mouth and eye sockets begin to form. The respiratory system actively develops, the heart begins to divide into chambers and arteries, and the spleen and gall bladder are formed.
At week 8, ultrasound can record the first movements of the embryo.
At week 9, the fingers on the upper and lower extremities are visible, although they are still webbed. This period is characterized by the fact that the placenta begins to supply the embryo with nutrients and take away waste products. The embryo already has taste sensations.
At week 10, the membranes between the toes disappear and the tail disappears. The gender of the child is still difficult to determine at this age, but boys are already beginning to produce testosterone.
By the 11th week, the embryo weighs 5 g and measures 3 cm. This is the final stage of embryonic development; the embryo will subsequently be called a fetus.
Intrauterine development of a child by week in the second trimester of pregnancy
At 12 weeks, almost all organs of the fetus have formed and the child begins to actively move inside the uterus.
This is the beginning of the third period of fetal development. At this time, as a rule, an ultrasound is performed, which determines the quality of the child’s development and genetic abnormalities.
If intrauterine abnormalities are detected in the fetus, the woman is recommended to undergo additional tests. But final conclusions about chromosomal abnormalities can be made at 20 weeks with a control ultrasound. If serious pathologies are confirmed, doctors recommend terminating the pregnancy.
It is also worth noting that the older the parents, the higher the risk of developing pathologies in the child. However, in this case, the opposite may be true: the percentage of talented children born is higher among older parents.
At week 13, the external genitalia differentiate. However, they can be distinguished already at 14-15 weeks using ultrasound. At this stage, the formation of the intestines occurs. The baby receives nutrition through the umbilical cord.
From the 14th week, the baby’s skeleton begins to form, which was previously represented by cartilage. The length of the arms corresponds to the proportions of the body, and the legs are formed with some delay. The baby can yawn and suck his thumb. He perceives the vibrations of sounds, distinguishes well the timbre of his mother’s voice and music.
That is why it is important for expectant mothers to listen to beautiful classical music, thus instilling in the baby good taste.
At week 15, the blood vessels of the fetus become noticeable, visible through the thin skin. The skeleton and bone marrow continue to form.
At 16 weeks, a routine ultrasound is performed, where you can notice the movement of the baby's eyes. The legs have become proportional to the length of the body and small nails begin to grow.
At 17-18 weeks, the small body is covered with primary fluff - lanugo. This is a natural lubricant that protects the skin from the aquatic environment. During this period, fingerprints are laid, which are genetically predetermined.
The baby weighs 200 g and is 14 cm tall.
At 19-20 weeks, fetal growth begins to slow down somewhat. At this stage, subcutaneous fat is deposited, which keeps the small body warm. The respiratory system is improving more and more, but it is not yet able to function independently.
Mid-pregnancy: intensive fetal development
Starting from the 20th week, the baby's teeth begin to form. The baby's hairs on his head grow more actively, but their pigment is formed a little later.
From 22 weeks, mothers begin to feel the baby pushing. His weight at this stage is 450 g, and his height is 19-20 cm.
From 23 weeks the baby begins to gain weight. The child begins to see, he even dreams. The brain is actively developing.
The muscular system and internal organs continue to actively improve. The respiratory system is becoming increasingly developed. The first feces - meconium - accumulate in the baby's intestines.
The baby's skin is red and wrinkled. The child actively reacts to the position of the mother’s body and to external sounds. Taste buds have already formed on the tongue, thanks to which the child develops food preferences. It is important for mothers to understand this and try to avoid spicy and bitter foods, since the little one prefers sweets.
The beginning of the third and final trimester is week 27. By this time, all the organs of the fetus have already formed, and in the future they will be improved, as well as the development of the brain.
At week 29, the baby’s immune system is formed. The heart rate reaches 120-130 beats per minute. The baby may hiccup, as evidenced by slight tremors to the mother.
A child born at this stage can survive with certain care. His height is 37 cm and weight is 1150 g.
Prenatal development of the child in the last stages of pregnancy
Women who are preparing to become mothers healthy baby, of course, it would be superfluous to talk about in the right way life. Alcohol, cigarettes, lack of routine, sleep and rest have a very detrimental effect on the health of the unborn child.
At 30-32 weeks, the baby’s subcutaneous fat layer becomes thicker. Some babies are already turning head down at this stage.
Convolutions appear on the surface of the small brain. The pupils can already detect bright light. When performing an ultrasound at this stage, you can notice how the baby closes its eyes from bright light. For this reason it is important to avoid ultraviolet rays and give up a beach holiday.
From the 33rd week, the little man already becomes cramped in his mother’s tummy. At this stage, the fetus turns head down, preparing for birth.
If premature birth occurs at this stage, the baby has every chance of survival. However, he will be considered premature and will need special care in the hospital.
The baby's skin becomes pink and not so wrinkled, thanks to subcutaneous fat. It makes up 8% of the total body weight.
Thanks to the appearance of marigolds, the baby can scratch himself. Some newborns are born scratched.
From the 37th week there is an active improvement of the respiratory system. Babies born during this period can already scream. The vellus hair on the body thins, and on the head it grows rapidly. The child gains 30 grams of fat every day.
By this time, the stomach drops, and it becomes easier for mom to breathe. This usually happens two weeks before birth.
By this time the baby is ready to see the light. He is very cramped inside his mother: his knees are pressed tightly to his chin.
At week 39, the body becomes clean: the fluff remains only on the shoulders. The baby's intestinal system is filled with meconium and amniotic fluid.
At 40 weeks, prenatal development ends and a new person is born! Photos of newborns become almost the most important photo in the house. After all, what could be more exciting and beautiful than the birth of a small miracle!
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Every pregnancy is the same for a woman, but feels different. This is due to her state of health and emotional and psychological state, social conditions of stay and the characteristics of the development of the fetus. Each stage of pregnancy is characterized by certain changes in the development of the fetus in the womb. What changes are we talking about, how the child grows and develops throughout pregnancy - we will talk about this in this article.
Pregnancy is an interesting and difficult period in a woman’s life. At this time, the birth and development of a new life occurs in her, her body experiences a heavy load, which gradually increases with each month of pregnancy. A pregnant woman experiences physiological and psycho-emotional changes, and her tastes and preferences may also change. All this is closely related to the stages of intrauterine development of the fetus, which grows, develops and is actively preparing for its birth.
Fetal development: stages and features
In the womb, a child develops over 9 months, or 280 days. The process of fetal development does not occur chaotically, but according to an algorithm written by nature itself and provided for by the peculiarities of human anatomy. Development of all 
organs and systems of the fetus occurs in a strict order and within a certain period of time.
Medicine divides pregnancy into three important stages - trimesters, each of which is characterized by the growth and development of certain systems/organs in the body of the unborn child. All stages are also divided into weeks, since the condition of the fetus changes weekly. We will look at the features of each trimester.
From one cell, trillions of new cells are formed in 38 weeks. There are more than 200 types of them, and they are the biological building material necessary for the growth and development of a child in the womb, his birth and a full life on earth.
I trimester
In the first trimester, a woman exhibits the first signs of pregnancy, when the process of fertilization of the egg occurs, its movement and fixation in the uterine cavity. During this period, the formation of the vital systems of the unborn child occurs. This trimester is considered very important for the fetus and mother, so a woman needs to take care of herself and take care of the health of her unborn baby.
According to obstetric dates 
During gestation, fetal development in the trimesters can occur differently in different women. This is due to many factors - hereditary, social, physiological, psychological and other circumstances that can affect the health of the mother, the course of pregnancy and the development of the fetus.
This is a period when a woman may suffer from early toxicosis, she may feel drowsiness, general malaise, dizziness, etc. What changes the fetus undergoes in the first trimester during its development can be seen in Table 1 below.
Table 1
| A week | Fetal development |
| 1 | Development of the egg, ovulation, fertilization, birth of the blastocyst. |
| 2 | The movement of the blastocyst into the uterine cavity, where it will gain a foothold and continue its development. |
| 3 | The embryo takes on the shape characteristic of a human fetus. Nerve cells form the neural tube - the basis of the future spinal cord and brain of the embryo. The heart is formed, which until this moment resembled a clot of muscle cells. The size of the embryo's heart does not exceed the size of a poppy seed. One cell suddenly contracts, setting all the heart cells in motion through a chain reaction. The embryo's heart beats 20-25 times per minute and is necessary for the embryo, since without it the complete and correct distribution of oxygen and food is impossible. Blood cells are still primitive, but with each heartbeat they circulate through the thinnest (thinner than a hair) blood vessels, delivering the necessary building material and oxygen to each cell of the embryo. |
| 4 | The period when a woman can feel pregnant due to changes in her hormonal system. The embryo is no larger than a bean, but every day it grows by 1 mm. Two black dots appear in the area of his head - these are future eyes. The embryo’s heart is still single-chambered and miniature, but it already beats 80 times per minute, accelerating the pace with each new day. “Kidneys” appear on the body of the embryo; in the future, arms and legs will form from them. From the neural tube of the embryo, areas of the spinal cord and brain - the future central nervous system - are formed. The tissue growing from four sides forms the face. Its upper part grows down, forming an area for the formation of the nose and chin. The cheeks are formed by tissue on both sides, forming the upper lip. Its connection is called the “philtrum”, and it is preserved - it can be seen on the face of an adult. Improper fusion of this tissue contributes to the formation of a defect known as a “cleft lip.” After birth, a baby with such a defect will need the help of a surgeon. The human embryo is not much different from the embryo of any other animal. Only 1.5% of genes indicate that this is a human embryo. |
| 5 | The first heartbeats of the embryo begin to be heard. Its size is only 3 mm, but it already shows signs of the formation of the lungs, heart and thyroid gland. |
| 6 | The formation of the spine, upper/lower limbs and two hemispheres of the brain occurs, and the intestines are formed. The embryo stretches, its length is 20 mm, and its body takes on the appearance of a human embryo. The eyes are formed from black dots; they are widely spaced and not yet equipped with eyelashes. Head size still dominates relative to body size. At the time of birth, the baby's head will make up almost ¼ of his body, since the remaining parts will not be able to keep up with the growth of the head. |
| 7 | The organs of vision develop, the organs of hearing are formed (on ultrasound, the appearance of auditory elevations, eye sockets, and nasal folds is observed). An ultrasound can already clearly determine the presence of interdigital spaces; the formation of future fingers of the lower/upper extremities is taking place. The length of the embryo is 6 mm. |
| 8 | Noted active growth embryo, the formation of facial features, the nose and ears are clearly distinguishable, the neck is visible. It can already be called a fruit, and in appearance it looks more and more like a person. This is an important stage in the life of the fetus. Previously, he received nutrients through the yolk sac, a floating ball connected to the umbilical cord. Unlike a chicken yolk, the human yolk sac contains no food reserves; in the first days of pregnancy, it produces blood cells necessary to nourish the embryo. At this stage, it is unable to provide the fetus with the required amount of food, so the placenta becomes the source of nutrition for the fetus. It is connected to the umbilical cord and attached to the wall of the uterus. The placenta is a complex system that supports the intrauterine life of the fetus, consisting of an extensive network of tiny blood vessels. They are attached to the wall of the uterus and with their help the fetus, through the umbilical cord, draws from the mother’s body all the useful substances it needs: water, oxygen, proteins, etc. The fetus also excretes its waste products through the placenta. |
| 9 | At the beginning of the week, the length of the fetus is from 15 to 20 mm, the weight is 3-4 g, and at the end of the week these parameters almost double. The placenta controls the pregnancy process by producing the necessary hormones in the mother's body. The placenta acts as a filter, preventing harmful substances from reaching the fetus, but it is also unable to cope with some types of them. For example, alcohol, smoking products and many medications easily pass through the placenta to the fetus. In most cases, the mother's body tells her which foods her unborn child needs and which are dangerous for him. The active development of the nervous system of the embryo is observed when the body of the previously immobilized fetus begins to twitch as a result of the occurrence of nerve impulses and reflex convulsions that are not yet controlled by the brain. Movement of the fetus is necessary to stimulate muscle growth and strengthen ligaments. The brain is not yet able to control the work of the heart, which beats automatically. Its maximum speed is 157 beats per minute. |
| 10 | The brain begins to control all vital systems of the fetal body, slowing down its heartbeat. He also now controls the movement of the upper/lower limbs. The development of the sucking reflex is noted. |
| 11 | In the period from 6 to 11 weeks, the embryo undergoes important metamorphoses, its body increases almost 5 times. At the same time, the formation of more than 200 types of different cells occurs: nerve, muscle, liver, kidneys, stomach and other cells that make up the human body. All parts of the body characteristic of a person are formed. Embryo growth – 7 cm. The fetal central nervous system continues to develop, forming its response to touch and breathing. |
| 12 | The size of the embryo is no larger than the mother's fist, but it is already more adapted to the environment in which it is located and less sensitive to various stimuli. The risk of his premature birth is reduced. The skeletal system is strengthened, and all systems and organs of the fetus further develop. |
All characteristic features of the human body (muscles, ribs, organs, heart, etc.) appear in the fetus during 9 weeks of the first trimester of intrauterine development.
For the development and health of the unborn baby, the first trimester is the most difficult and dangerous. Any 
a malfunction in the mother’s body can affect the intrauterine development of the fetus. The 3rd and 4th weeks of pregnancy are considered the most critical - during this period the process of implantation of the fertilized egg in the uterine cavity and the formation of the central nervous system of the future fetus occurs. A common cold, infection, exacerbation of a chronic disease, nervous breakdown, stress, excessive physical or psychological stress - all this can cause a woman’s hormonal system to malfunction and provoke a miscarriage.
From the last week of the first trimester, the fetus is able to distinguish some sounds. From now on, every week he will hear better, react more actively to the touch of hands on his stomach, to his mother’s voice. In the second trimester, gynecologists and psychologists recommend that pregnant women talk to their unborn child, listen to calm and pleasant music, and the sounds of nature. It is believed that the baby in the mother’s tummy hears everything and feels her mood, feels the attitude towards herself both from the mother and from those people who surround her.
II trimester
The second trimester covers the period from 13 to 27 weeks of pregnancy. In most pregnant women, toxicosis passes by this time; the size of the tummy still allows free movement and wearing. ordinary clothes, which will soon have to be replaced with dresses and sundresses for pregnant women. A woman’s well-being in the second trimester usually does not cause concern to the doctor if the pregnancy is not burdened by any developmental pathology. From 20 or 22 weeks of pregnancy, some women are advised to wear a maternity bandage to help support 
growing belly, reduce pain in the back and hip joints.
By the beginning of the second trimester, the baby in the mother’s womb weighs on average no more than 30 g, and its height is about 10 cm. By the beginning of the third trimester (at 27 weeks), the fetus’s growth will be almost 35 cm, and it will weigh about 1.2 kg. The fetal skeleton is already quite well formed, so in the second trimester its brain and muscular system will actively develop. There is high mobility of the baby in the mother's womb, and between 18 and 22 weeks a woman can clearly feel the first movements and tremors of her unborn child. From Table 2 you can see what changes occur in the fetus’s body during the second trimester.
table 2
| A week | Fetal development |
| 13 | The gender of the unborn child is still difficult to determine, but a competent ultrasound diagnostician will be able to recognize it. In boys and girls up to the 13th week, a bulge is formed instead of the genital organs - the angle of inclination at which this bulge is located helps the doctor to reveal the secret of the embryo’s gender. The gender can be more clearly recognized at the 15th week of pregnancy, but the formation of the genital organs in the embryo has already begun. The formation of baby teeth and the development of muscles that provide the sucking reflex are also noted. The baby is already able to move his lips. In boys, the genital organ is clearly visible on an ultrasound; their body begins to produce testosterone (male hormone), the formation of the prostate gland (for boys) or the formation of an egg (for girls) begins. The first hairs appear on the skin of the fetus (just above the eyes and above the lip). A unique pattern is “drawn” on the skin of the fingers of the unborn child. |
| 14 | The formation of sexual characteristics and intestines continues (with the presence of villi on its mucosa). Men's testicles are already capable of producing testosterone, and women's ovaries are already capable of producing eggs. The pancreas begins to produce the hormone insulin, and processes take place in the liver and spleen in which the blood cells of the unborn baby are formed. |
| 15 | The first layer of hair appears on the fetal body - fluff. The baby makes his first attempts to “breathe” on his own: the embryo breathes amniotic fluid. Now his gallbladder is starting to function. This week, a woman who has had previous pregnancies may feel fetal movements for the first time. The weight of the unborn baby is already 130-160 g, his height is 12-14 cm. |
| 16 | Ossification of the skull and strengthening of the fetal muscular system are observed. There is an increase in his motor activity (the woman may not yet feel the movements and shocks of the fetus). The sex of the unborn child is already easily determined by ultrasound. Changes occur in the proportion of the fetal body - the size of the head decreases, its lower/upper limbs lengthen, the fingers/toes separate from each other, and nail growth begins. The arms develop faster than the legs, perhaps because they act as important sensory organs and develop at the same time as other organs. The distance between the eyes has decreased, giving the baby's face a human appearance. Central nervous system functions, it has expanded and controls all parts of the fetal body, whose movements have become more diverse. The muscles acquired the necessary flexibility, the baby’s movements in the womb became softer and smoother. The brain completely controls the baby’s body, whose heart no longer beats spontaneously and convulsively - its work is controlled by the brain. The heart makes no more than 140-150 beats per minute. The weight of the fetus is 180 g, and its height is 14-16 cm. |
| 17 | The formation of the placenta is completed. The baby in the womb begins not only to hear, but also to distinguish the noises/sounds that surround him. His nervous system improves, he becomes sensitive to touch, sounds, light. The fetus is too mobile, makes many complex movements and maneuvers, trying to find a comfortable position. The fetus's joints bend easily, opening up the space inside the mother's womb in a new way. By swimming and maneuvering, the baby learns to maintain balance and coordination. In the womb, the future person develops the ability to control position and behavior own body in space. The fetus is in the process of forming subcutaneous fat, which participates in the body’s heat exchange processes. |
| 18 | This week marks the end of the formation of the child’s immune system. His digestive system is already formed and developed so much that it is ready to function. The baby makes swallowing movements, swallowing the amniotic fluid in which it swims. The kidneys and digestive organs are already working - some of the undigested particles will be deposited in the intestines, the remaining processed products will be excreted in the form of urine into the amniotic fluid. Some babies can already open their eyes at 18 weeks, while others will only be able to do this at 24 weeks. This is how the blink reflex develops. The baby gets to know himself and the environment and moves actively. He feels himself with his fingers, touches the walls of the uterus, pushes off with his legs, jumps and turns over. He needs these skills because they are a kind of training before birth and passage through the birth canal. The grasping reflex develops well, although its significance is unclear: it is hardly useful for the survival of a newborn. |
| 19 | The movements of the fetus are more conscious, since the connection between the muscular and nervous systems is almost completely formed. A woman may first feel fetal movement at the end of the 18th or early 19th week. The baby has grown to 18 cm, his body is covered with soft hairs that will disappear by the time he is born. Molars are formed. They will begin to grow in the child when his baby teeth are replaced with permanent ones. The fetus receives sugar and water from the mother's amniotic fluid; a small portion of hydrochloric acid and some digestive enzymes are already present in its stomach. Nutrients enter his body through “breathing” and through the placenta. He receives some of them by swallowing amniotic fluid. |
| 20 | This week, the fetal body reaches the proportions that are characteristic of babies, the ratio of its head to the rest of the body is evened out. Since its fat layer is not yet fully formed, the fetal body appears thin, but the baby is active and feels normal. He is halfway through his birth. His height is already 19 cm, body weight is 300 g. |
| 21 | The baby grows and gains weight, accumulates subcutaneous fat, and his mother often begins to feel hungry. A layer of special lubricant is formed on the child’s body, protecting his skin from the effects of amniotic fluid. This week his body weight reaches 350 g, and his height increases by 5-6 cm. |
| 22 | There is high motor activity of the fetus: the baby can change its position in the mother’s womb several times within one day. He eats, sleeps, moves - continues to explore himself and the space around him, gain weight and grow. The baby sucks his finger and can already turn his head to the side. |
| 23 | The weight of the fetus can reach 500 g. Its heart sounds are well audible with an obstetric stethoscope. Twitching of a baby's eyelids, which are visible on an ultrasound, indicates that his brain is functioning correctly. The baby may be more awake if the mother is on the move, and when she is nervous, she behaves restlessly. The baby's hair begins to darken because his body has already begun to produce a special pigment. If the baby is born prematurely, he already has a chance to live, as well as the risk of problems with brain functions. |
| 24 | The child is still active, but his growth slows down slightly at around 30 cm, and his body weight begins to increase and reaches 600-700 g. The baby opens his eyes for the first time and is able to distinguish daylight from the darkness of night. His eyebrows and eyelashes are already beginning to appear, and his face takes on the features of a newborn baby. His lungs are developing well and he is trying to “breathe.” A baby born at 24 weeks has every chance of survival. At this stage, a woman needs to rest more and receive only positive emotions so as not to provoke premature birth. In case of premature birth, the baby has a chance to survive thanks to modern equipment and the experience of neonatologists. |
| 25 | All the baby’s organs and systems are already functioning and at the same time continue to develop further. His heartbeat can be heard without a stethoscope by placing his ear against a pregnant woman's belly. The child’s skeleton becomes stronger, and the baby’s kicks in the mother’s stomach are more noticeable to her. |
| 26 | The baby's lungs can barely cope with the task of supplying oxygen to his organs. With a lack of oxygen, the baby freezes, trying to move less, so the mother needs to walk more. fresh air, do not smoke, ventilate the room more often. Almost half of children born before 26 weeks have brain defects and problems in development and learning. Starting from this week of pregnancy, the baby is actively developing all the senses: eyes, ears, taste buds on the tongue. The child learns to recognize the signals sent by the impulses of his central nervous system. |
| 27 | Hair begins to disappear from the child's skin. The proportions of his body correspond to the proportions of a newborn baby, but the total mass is still not enough. His endocrine system begins to function, producing growth hormone. The baby's respiratory muscles develop. Its height is 32-35 cm, body weight reaches 1000 g. If a mother has a premature birth, the baby has every chance to survive and grow up to be a healthy, full-fledged person. |
The second trimester is a period in which the active development of all systems/organs of the fetus occurs, the baby himself also grows and gains weight. He begins to actively move in his mother’s stomach and make himself known. It has its own wake and sleep patterns. He hears almost all sounds happening around him, distinguishes between darkness and light.
To a woman staying 
in the second trimester of pregnancy, you need to walk outside more often, ventilate your room, and eat more vegetables and fruits. She must diligently maintain personal hygiene and not neglect morning exercises for pregnant women, try not to be nervous and not to take negative events to heart.
During this period, a woman is recommended to enroll in a course for a young mother, where she will learn about the features of pregnancy in the last trimester, the correct behavior of a mother during childbirth and caring for a child in the first days after birth. She should also not forget to visit her gynecologist and inform him about all the changes that occur in her body.
III trimester
The last trimester for the expectant mother will not be the easiest, since her tummy has already grown quite enough. It becomes difficult for her to move, sit up, bend over, or roll over on her side in bed. It is impossible to sleep or rest on your back due to difficulty breathing and a feeling of constriction in the internal organs. Many women are afraid of the onset of labor and 
in the last trimester they begin to get nervous - these experiences can lead them to stress. At this time, advice and reassurance from those women who have already successfully completed childbirth is important for a pregnant woman.
As for the baby, he feels great. All his organs are already formed, he breathes on his own, hears perfectly, and is able to distinguish tastes. The baby actively kicks its legs, rolls over, and spins in all directions in the mother’s womb. Its head is already beginning to be covered with hairs, its body is covered with lubricant, which will make it easier for it to pass through the birth canal. The fetus is preparing for release, because it will soon be born. What changes occur with the baby in the third trimester of the mother’s pregnancy can be seen in Table 3.
Table 3
| A week | Fetal development |
| 28 | The baby's weight is from 1000 to 1300 g, his body length is from 35 to 40 cm. The baby not only hears sounds, but also reacts to them, showing mom with pushes what he likes and doesn’t like. |
| 29 | The baby's kidneys begin to function, releasing up to 500 mg of urine per day. The adrenal glands produce androgen-like substances, and the baby’s circulatory system produces red blood cells. The baby is actively moving inside the uterus, where it becomes cramped. He gradually turns over, taking a position in which it will be easier for him to pass the birth canal. The fat layer allows the baby’s body to independently solve the problem of body thermoregulation. His skeleton has become stronger, but the bones of the skull have not yet fused completely - this feature will allow his head to squeeze through the birth canal at the time of birth. |
| 30 | The baby begins to rapidly gain weight, his height reaches 35-37 cm with a body weight of 1000 to 1400 g. His brain has reached the stage of development when the baby is already able to analyze and remember some information. At this stage, the baby’s teeth are covered with a layer of enamel. His body is cleansed of a special lubricant that protects his skin from the effects of amniotic fluid. The baby swallows this liquid, and his digestive system processes the contents of the stomach. The undigested particles will form the newborn's first stool, meconium. At the end of the 8th month, the baby’s body weight reaches 1500 g, his height ranges from 37 to 40 cm. |
| 31 | The baby continues to practice “breathing exercises”, preparing for his first breath outside the mother’s womb. His eyes are often open, he squints in response to bright light. All newborns have blue eyes; only a few weeks after birth their color will begin to change. The baby grows stronger, his skin becomes thicker, acquires elasticity and a characteristic bright pink hue, since there is already the necessary fat layer underneath. There is not enough subcutaneous fat yet, so a network of capillaries and vessels is visible under the skin. The height of the fetus reaches 40 cm with a body weight of about 1600 g. |
| 32 | Premature birth is no longer scary for the baby: he will be born with a body weight of 1500 to 2000 g and will be quite viable. True, his lungs are not yet well developed, and many of the reflexes he needs to survive are missing. The baby's face is cleared of wrinkles, smoothed out, and hairs grow on the head. He quickly gains body weight due to the production of immunoglobulins. During this period, some babies begin to gradually turn head down - this is the position the fetus should take before labor begins. The baby moves more, disturbing the mother and causing her some inconvenience. To calm him down, a pregnant woman needs to lie down. A protruding navel should not bother the mother: this is the result of pressure and a large load on the mother’s body. After childbirth, the navel will take its previous appearance. The child’s body weight at 32 weeks is 2000 g, height is from 40 to 42 cm. |
| 33 | At week 33, a woman is usually prescribed an ultrasound to determine how developed the fetus is, whether its development corresponds to the gestational age, and whether there are any pathologies in development. The baby’s brain is already formed, the number of neurons increases, expanding nerve connections. This week, the heart begins to gain weight, and the subcutaneous fat layer grows. The baby needs more nutrients, and he persistently demands them from his mother. |
| 34 | · The sucking reflex is developed - the child sucks his thumb, training to suck on the mother's breast. · His skeleton is getting stronger, and the body needs more and more calcium. The baby moves a lot: the uterus is already cramped for him, he tries to find a comfortable position, turns over and pushes. · The lungs are ready to receive oxygen, but are not yet 100% able to function independently and fully. · The baby weighs up to 2400 g, and his body weight is 40-45 cm. |
| 35 | · The baby’s skin acquires the required color and texture, is cleared of grease, and becomes less transparent due to the accumulation of subcutaneous fat. The fluff on the baby’s body is no longer noticeable and has almost disappeared. · The development of the adrenal glands continues, and growth of the nail plates is observed. · The baby's ears are already fully deployed and correctly positioned. · There is already some original feces in the intestines of the fetus - meconium, which will be the baby's first bowel movement after birth. · The baby weighs from 2000 to 2600 g, its body length can vary from 40 to 45 cm. |
| 36 | The baby's skin is smooth, small amounts of vellus hair may remain on his back and shoulders, but it will disappear in the first days after the baby is born. The presence of a sucking reflex indicates that the baby is ready to feed at the mother's breast. A baby's fully formed heart beats steadily, but there is still a small hole between the atria. When the baby takes his first breath outside the womb, it will close. Usually this week the baby is already positioned correctly - head down. He spins inside his mother’s belly, twists his legs and pushes, but by the time of birth he must take the correct position. The baby’s body is rounded, his nervous, immune and endocrine systems continue to improve. In general, the baby is almost ready for birth. Its weight at this stage of development ranges from 2500 to 3000 g, height – from 43 to 47 cm. |
| 37 | The child’s reproductive system is established, the ovaries (in girls) and testicles (in boys) function and produce the necessary hormones. The baby’s body is covered with vernix, the accumulation of subcutaneous fat continues: on average, its increase per day is about 30 g per day. His skeleton has become stronger, the cartilage has become harder and denser, and the ligaments are stronger. The baby continues training in independent breathing: after birth, he will have to inhale air for the first time, and not amniotic fluid. |
| 38 | At 38 weeks the baby is fully viable. A child born at this stage may have some difficulty breathing, but overall he is absolutely healthy. If he is born this week, he will need health care and a drug that will help him breathe fully. Its body weight is from 2700 to 3200 kg, its height can reach 45 cm. |
| 39 | · All the baby’s organs are developed, all systems function normally. If there are any minor deficiencies, even with premature birth they can be easily eliminated. This week, the child’s body completes the construction of its own body, and the brain completely controls this process and the functionality of each system. The baby's hair on the head can grow by this time from 1-3 to 7-9 cm. |
| 40 | · This last week of pregnancy for the baby proceeds without any special changes. He is ready for childbirth, for his first breath and meeting his mother. He tries to take the correct position (head down) and waits for labor to begin. · The baby’s bones at the time of birth are not yet ossified and soft: this feature will help him pass the birth canal more easily. A large amount of norepinephrine and adrenaline can be found in his blood. These substances will support his body during childbirth, if this process drags on and the baby experiences oxygen starvation. · There is a slight increase in the level of sugar in his blood and an increase in heart rate. All this indicates the proximity of childbirth. · The baby’s body length in the last week of pregnancy can range from 45 to 54 cm, body weight also varies between 3200-4100 g. · By the end of the week, the baby will turn his head down, press his knees to his body in readiness to leave the place where he has been warm, cozy, nourished and calm for all 9 months. · Intrauterine development of the fetus is now complete. |
Pregnancy is a complex physiological process that occurs in a woman’s body, during which the development of a fetus from an egg occurs, ending with the birth of a new person.
Very often during a woman’s pregnancy, all the attention of her loved ones is focused on her. Everyone tries to help her with something, fulfill her desire, protect her from worries and illnesses. The main thing is for loved ones to understand that the health and well-being of the mother determines the health and life of the unborn baby.
Nature itself will cope with what is entrusted to it: the child will grow and develop in the mother’s womb. The task of a pregnant woman and her environment is not to harm the child even before he is born. And then, after 9 months, to the delight of all family members, a strong and healthy baby will be born.
Knowing how the fetus develops week by week during pregnancy, you can monitor the health of mother and baby. The doctor monitors whether the woman’s physical and psychological sensations coincide with the norms. This allows you to react in time and help mother and baby if necessary.
The expectant mother is calmer if she knows that the changes in her body are going according to plan. It is useful to know how the fetus develops by week of pregnancy. So mommy knows in advance what to expect, what to prepare for. Can tell the doctor if something doesn't go according to schedule.
How to correctly determine the onset of pregnancy
To track your pregnancy week by week, fetal development and sensations, you need to know what time to count from. How to determine the onset of pregnancy:
- if the mother knows when conception occurred, this is the most accurate option;
- The doctor determines the pregnancy period when he determines the size of the uterus, but in the first weeks it will not be possible to determine the period in this way, the uterus is still too small;
- by the date of the first day of the last menstruation, the date of conception is determined quite accurately, from this time the uterus begins to prepare for pregnancy;
- From 4-5 weeks you can conduct an ultrasound examination, it allows you to very accurately determine the period of the crumbs in the tummy.
Let's look at how the fetus develops over the weeks of pregnancy and a description of the changes in the small body. We'll tell you everything about pregnancy week by week.
Fetal development by week of pregnancy (photo)
1 Week
The obstetric week is not counted from the moment of conception, but from the last day of menstruation. At this time, the body is only preparing for a possible conception. If fertilization occurs during this period, slightly spotting spotting may be observed.
2 week
This time is considered the most favorable for conception. If a woman’s body is healthy and there are no pathological processes, then by the second week of the cycle the egg is mature and ready for fertilization. If conception has occurred, then at this time the fertilized egg attaches to the uterus, and from this moment the development of the fetus begins.
3 week
The embryo is still tiny, it is fixed in the uterus, and the formation of sexual characteristics is laid down at the cellular level. The placenta begins to form.
4 week
At this time, pregnancy can be determined by tests. The size of the embryo is no larger than a poppy seed, weighing about 0.5 g. The cells divide every minute, the crumb grows. During this period, the mother’s mood may change dramatically. Drowsiness is common. Increased sensitivity to odors appears. In the morning you may experience nausea and dizziness.
5 week
The baby at this stage looks a little like a tadpole: it has a small body and a large head. Its size is about 1.7-2 cm. The formation of the spinal cord and brain is underway. In the fifth week, the baby's blood type was formed. The thyroid gland, intestinal and urinary systems begin to form. The baby's tiny heart begins to beat.
week 6
The head and torso of the unborn baby are clearly visible. Tiny processes appear - legs and arms. Hormonal changes in the mother’s body lead to the fact that hunger may often be felt or, conversely, an aversion to food may appear. During this period, the expectant mother may lose weight due to the onset of toxicosis.
week 7
The placenta is fully formed: it performs protective and nutritional functions.
Baby development:
- the body is approximately the same size as the head, while there is still a small tail on the tailbone;
- the nervous system is being formed, both hemispheres of the brain are already formed;
- the heart works, it consists of 4 chambers;
- blood circulation is improved, the placenta nourishes the baby with oxygen, supplies nutrients, it protects him from germs, bacteria, infections and toxins;
- skeletal tissue turns into bone, forms musculoskeletal system, the baby can bend his elbows and knees;
- the hearing system is formed, the rudiments of teeth are laid, a nose and nostrils appear, upper lip;
- the upper integumentary layer appears - the epidermis;
- a mound appears between the legs, which will later determine who is in the tummy: a girl or a boy.
8 week
By this time, almost all systems of the small organism have been established and their rapid development is underway. The tail is no longer visible. The baby can move his arms and legs and unclench his fingers. The eyes are now closer to each other, and the visual system is being formed. At this stage, the baby is already able to respond to touch.
Week 9
The arms and legs are well formed, the baby can move around in the amniotic fluid, he is still small and has not taken up all the space. The genitals are visible. The baby's eyelids have formed and he can blink involuntarily. The weight of the fetus is about 4 g, the height is about 3 cm.
10 week
The brain continues to develop. The head gradually rises from the chest. The fingers lengthen, although the membranes between them still remain. Sex hormones begin to be released, in boys - testosterone, in girls - estrogen.
11 week
The baby's weight is approximately 11 g, and his height is approximately 5-6 cm. The ears are formed and hair follicles are formed.
12 week
The fruit is about the same in length, about 12-14 g in weight. The intestines begin to contract, the gastrointestinal tract is trained. The baby tries to raise his head and may start sucking his finger. He already reacts to sounds and is sensitive to pain.
Week 13
The vocal cords are formed, the torso begins to actively grow, and the growth of the head slows down. The sense of smell develops. Reactions to changes in temperature, light, noise, and music appear. The baby can already sleep for a few minutes a day. The brain can issue commands through reflex movements. Villi appear in the intestines. The skin is thin. Weight - about 20 g, height - up to 8 cm.
Week 14
The baby's weight is up to 50 g, height - up to 10 cm. Wakefulness and sleep modes appear. The respiratory system is being trained. Insulin begins to be produced. The baby’s heart reacts to mother’s stress, so you need to learn to calm down for the sake of yourself and your baby.
Pregnancy by week (fetal development with photos)
Week 15
Vision has been formed, now the baby will be able to see after it is born. He distinguishes between light and darkness. The sweat glands are working. Hairs begin to emerge. The process of ossification of the skeleton has begun, it will require a large amount of calcium from the mother.
Week 16
Now the fetus has taken on all the contours of a baby. The skin is still thin, it is covered with light fluff, and the blood vessels are clearly visible under it. The weight of the fetus is 110 g, height is 11-14 cm. The chemical composition of the blood changes, lymphocytes, erythrocytes, and platelets appear. Hemoglobin synthesis is in progress. Eyebrows and eyelashes are visible on the face. The entire body of the fetus is covered with white lubricant; it protects the baby’s skin until birth.
Week 17
The baby is sleeping more and more. When he wakes up, he can stretch. The baby is very sensitive to sounds. He dislikes sharp and loud sounds. And his mother’s voice calms him down. Girls' internal reproductive organs begin to form this week. This week the strength of the baby’s kicks increases, they are frequent and noticeable.
Week 18
You can already feel the baby's first kicks. His musculoskeletal system is actively developing. Subcutaneous fat is gradually formed, muscles continue to develop, and the skeleton becomes increasingly stronger. The weight of the crumb is approximately 150 g, height is up to 14 cm.
Week 19
The baby sleeps up to 16-18 hours a day. The main sense organs are improved. The amount of subcutaneous fat increases. The respiratory system develops and strengthens. Weight reaches 200 g, height - up to 14-15 cm.
Week 20
With an ultrasound, you can see the gender of the baby, his face, and facial expressions. The baby is already yawning, tumbling, playing. The legs have become longer and more proportional, the head is now smaller compared to the body. The skin thickens: it now consists of four layers. Marigolds appear on the hands and feet. The head is covered with the first hairs.
21 weeks
When the baby moves, this can be seen on the surface of the tummy: tubercles appear on it. The baby’s weight is up to 330-350 g, height is up to 26 cm.
Week 22
The baby sleeps a lot, and even turns over actively in his sleep. The nervous system is improved, neurons are fully formed. Weight - approximately 410 g, height - up to 28-30 cm.
Week 23
The baby enters the REM sleep phase - now he can dream. The respiratory organs are not yet formed, but the baby begins to do the first test exercises. Weight reaches 400-420 g.
Week 24
Height - up to 25 cm, weight - up to 500 g. Oxygen enters through the umbilical cord, but the baby already knows how to inhale and exhale. The brain is formed, neural connections increase. The baby plays with the umbilical cord, makes faces, frowns and sucks his finger.
Week 25
The production of pigment begins in the child's hair. The baby can clench his hands into fists. He develops a grasping reflex. The weight of the crumb is 700 g, height is about 30-35 cm.
Week 26
The baby is gaining weight, now he is about 1 kg, his height is 33-35 cm. Subcutaneous fat accumulates, the skin becomes lighter. The baby becomes stronger, his kicks can cause discomfort to the mother.
Week 27
A child's brain grows and develops. The foundations of thinking are laid: memory and attention. Calcium is still needed in sufficient quantities, because the bones have not yet fully formed. Subcutaneous fat accumulates and skin color changes. The placenta forms the baby’s first immunity, which will protect him for the first six months.
Week 28
Subcutaneous fat accumulates, wrinkles are smoothed out, and the skin brightens. Convolutions are formed in the brain, intelligence is formed and grows, and emotions appear. This week, a Rh conflict between the fetus and mother is possible, so the doctor closely monitors this process and, if necessary, takes special measures. The baby's weight is about 1.3 kg, height is up to 37 cm.
We will tell you in detail what will await you from the beginning of the birth of a new life until the very birth.
Pregnancy is a special time that changes the expectant mother’s worldview, her values and priorities. Almost every woman faces certain difficulties while carrying a baby. To avoid them, it is important to have complete information about all the processes occurring in the female body at each stage of pregnancy.
Early pregnancy: first month
Most women do not even realize that they are pregnant, while very serious changes are beginning in their body. Pregnancy becomes known only at the end of the first month, and sometimes at the beginning of the second.
Doctors consider the beginning of pregnancy from the beginning of the last menstruation, although fertilization usually occurs after ovulation. Therefore, the concept of “obstetric period” is several weeks longer than the actual gestation time.
Changes in a woman's body
The first and second weeks of the month are the time when a woman is not yet actually pregnant, but her reproductive system is actively preparing for conception. In the first week, menstruation occurs as usual. If you are just planning to become a mother, then you should stop taking analgesics for menstrual pain: the chances of successful conception will be higher. In the second week, one of the eggs begins to mature.
By the beginning of the third week, at the moment, the strongest egg leaves a special bladder filled with liquid into the fallopian tube. 
Here the female reproductive cell will remain for several days, waiting for fertilization.
The so-called yellow body will begin to form. It will be responsible for the hormonal levels that are optimal for the development of pregnancy.
All that is needed now is fusion with the sperm. Two cells, connecting with each other, form a zygote - the future embryo. The zygote is miniature in size and moves freely throughout the uterus, only after a few days attaching to its wall.
To maintain the vital functions of the zygote, the mother’s body produces large amounts of progesterone. Because of it, a woman will feel heaviness in the lower abdomen and pain in the nipple area, as with PMS. The urge to urinate will become frequent, drowsiness and sensitivity to odors may occur.
Baby development at 1 month
During this early period, all the genetic information that shapes your baby’s appearance, character traits and predisposition to diseases is laid down.
The sex of the baby is also determined. There are two types of sperm: one carries the XX chromosome, the other carries the XY chromosome. The sex of the child will depend on which of them can get to the egg. If fusion occurs with the XX sperm, a female embryo will begin to develop; If XY sperm enters the fallopian tube, the couple will have a boy. By the end of the 4th week of pregnancy, the embryo has already completed its attachment to the uterine cavity and enters the embryonic stage.
The level of the hormone will increase, and now pregnancy can be determined using a simple pharmacy test.
Three areas are formed in his body, which will later become full-fledged organs and systems. Also this week, the formation of the chorion (future placenta) and amnion (fetal membranes) is completed. And your baby is still very small - the size of the embryo is only 0.5 millimeters.
- It is necessary to undergo an ultrasound scan as soon as there is a suspicion that conception has occurred. This will help to diagnose an ectopic pregnancy in a timely manner.
- At this time, taking vitamins A and E is useful. All pregnant women are also prescribed folic acid for proper fetal development.
- A complete abstinence from tobacco, alcohol and junk food is required. The expectant mother needs to walk in the fresh air as much as possible and get pleasant emotions.
Second month of pregnancy: changes in a woman’s body
At this time, the fact of pregnancy is already clearly established. There is a delay in menstruation, there should be no discharge. Any discharge with bloody impurities indicates the danger of embryo rejection, and in this case a visit to the doctor is required.
The first signs of early toxicosis appear. It is especially expressed in morning nausea and vomiting.
Problems arise in the gastrointestinal tract: heartburn, belching, constipation. These phenomena will stop only by the end of 3 months.
A serious test will be changes in psychologically. Your family should be sensitive to mood swings. But a pregnant woman should also try to control herself, because nervous tension not good for you or your baby.
The development of the corpus luteum reaches its peak, and by the end of this month the uterus will grow to the size of a large orange and can be easily palpated during examination.
Due to sprains, a woman may experience a pulling sensation in her sides and lower back.
Together with progesterone, lactogen, a hormone responsible for the development of the placenta, begins to influence the body. Their action reduces protein synthesis while increasing the production of glucose and fatty acids. This is necessary to compensate for energy expenditure on fetal development.
Baby development at 2 months
During this month, all organs and systems of the baby take their place. By the 5th week, his heart will make its first beats and blood vessels will appear. The organs of the respiratory and excretory systems will be formed. The brain is already beginning to respond to primitive reflexes.
The embryo still has a small tail, making it look like a small tadpole. The rudiments of facial features will appear on the fetal head: nose, eye sockets, ears.
In boys, the penis and testicles are identified. Now your future baby has moved from the embryonic stage to the fetal stage. Its physical dimensions are about 2.5 cm.
Seventh and eighth months of pregnancy
There is less and less time left until the moment of birth. Expectant mothers are going on maternity leave and are in search of a good obstetrician and maternity hospital. It is also worth deciding whether you want your husband to be present during the birth.
Feelings of a woman at 7 and 8 months
The production of the hormone relaxin increases, preparing your muscle ligaments for childbirth. Because of this, back pain appears, and it becomes more difficult for muscles and joints to stay in good shape. Your gait may become a little awkward, varicose veins become worse, and urinary incontinence may occur.
Also, the action of hormones increases the growth of body hair. After childbirth, they should disappear, so there is no need to deal with excess hair now.
By the end of the 8th month of pregnancy, the belly increases to almost its maximum size. Now the height of the uterine fundus will be up to 40 cm. Training (false) contractions begin, causing no pain at all. They prepare the uterus for real labor.
In many pregnant women, the nesting reflex is activated. You will increasingly want to devote time to making your home comfortable; willy-nilly, you give preference to viewing and reading materials for pregnant women.
Baby development at 7 and 8 months
Your baby has become very big, he is getting more and more cramped in the uterus. The fetus occupies a position that will remain until birth. If the presentation is unfavorable, you can perform special exercises to help “turn over” the baby.
All basic reflexes have already been formed. Bones are strengthened and the calcium content in them increases significantly. The lungs are completely ready to take the first breath.
By the last week of the 8th month of pregnancy, the fetus will weigh twice as much as at the end of the second trimester - 2.5 kg.
- The most dangerous thing that can happen now is the development of gestosis. If you have a headache, swelling has increased and your blood pressure has risen sharply, it makes sense to go to the hospital immediately.
- Once every two weeks you will visit the doctor and get tested. A full examination is required: measurement of the uterine fundus, fetal heartbeat.
- Swimming will help reduce the feeling of heaviness. They have a relaxing effect on the muscles and also calm the nervous system.
Ninth month of pregnancy: woman's feelings
You've reached the finish line! Although there is anxiety before childbirth, this month is the easiest for many mothers. It will literally become easier for you - your stomach will drop, which means the pressure on all internal organs will decrease.
Now your weight difference with the “pre-pregnancy” state is from 8 to 16 kg. The belly will no longer increase; on the contrary, visually it may become smaller. This happens due to depletion of amniotic fluid. 
You will experience for yourself what the harbingers of childbirth are. They will appear several weeks before labor (sometimes the warning signs appear several days before contractions). Among them are increased false contractions and the release of mucus plugs.
The problem of constipation disappears, but with pressure on bladder a constant urge to urinate begins to occur.
Fetal movements are noticeable less and less.
Your psychological attitude also changes. You will be characterized by slowness and absent-mindedness. Changes in mood are a consequence of anxiety before childbirth. Give free rein to your emotions, have fun or cry. Communicate more with your loved ones in the last weeks before the maternity hospital, because it is so important for you to feel their care.
Baby development at 9 months
The baby takes its final position, in which it will pass through the birth canal. His skin has a light tint, the fluff disappears, and the cheese-like lubricant remains in the folds of the body. The bones of the baby are quite hard; there is a fontanelle between the sutures of the skull. It will heal soon after birth. Thanks to the fontanelle, it will be easier for the baby to be born - the bones of the skull will be in a free position.
The child is completely ready for life outside the mother's womb. The lungs are ready to expand upon birth, the heart adapts to work in a new rhythm.
In the intestines of a newborn there is original feces (meconium), consisting of remnants of substances from the amniotic fluid.
1
In the last week of pregnancy, the mother needs to be very careful. It will be difficult for you to move, so you should walk with support if possible. Walk on stairs holding the railing tightly. 
2 Labor can begin at any time. You should always have your personal doctor's number handy.
Do not leave the house for a long time, or even better, take a walk only in the company of close people. Always carry with you a package of documents necessary for the maternity hospital.
3 Start packing your bags for the maternity hospital in advance at the beginning of the month. This way you will be sure that you have not forgotten anything important in a hurry.
So, the difficult time of pregnancy has come to an end. Now comes a new period, full of completely different worries and joys. Keep a positive attitude and you will definitely become the best mom!
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