Until what week does the fetal brain develop? Pregnancy

During this period, an organism emerges from a fertilized egg, possessing primitive structures of various systems and organs. Intrauterine development is divided into prefetal 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 fetal movements 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 premature, but mature.

In the last month, the lower extremities grow more rapidly, 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.

Nature gives only 9 months for a full-fledged child to form from one cell. During pregnancy, a woman may not feel the changes happening inside her every day.

The baby develops and grows every hour. In the first trimester, from the moment of conception until the 13th week, the main organs are formed: the heart, intestines, stomach and others. In the second trimester, until the 27th week, the organs mature and acquire a more complex structure. Finally, in the last, third trimester, that is, from the 28th week to the 40th, the child prepares for his birth.

Beginning of pregnancy

The woman, as a rule, has no idea that conception has occurred. However, immediately after it, the embryo begins to actively develop. As a rule, the expectant mother finds out that pregnancy has occurred at 4-5 weeks by doing a special test.

Should be clear, from what moment pregnancy begins to be considered. Most gynecologists use the date of completion of a woman's last monthly cycle as a starting point. This means that approximately 40 weeks of pregnancy begin on the first day after your last menstrual period. However, anatomy experts, in turn, talk about pregnancy and fetal development week by week from the moment the egg is fertilized.

Normal pregnancy lasts from 38 to 42 weeks . If the baby is born early than 37 weeks from the start of pregnancy, then they talk about premature birth. Conversely, if pregnancy lasts longer than 42 weeks, then they speak of late birth or chronic prolonged pregnancy.

First trimester

Fertilization of the egg, which occurs when sperm penetrate the egg through the membrane, is the beginning of pregnancy. Fertilization occurs in the Fallopian tubes, then the egg passes through them into the uterine container. Such an egg is called a zygote. After this, the zygote begins to divide into 2, 4, 8, 16, ... segments, and the process of forming an embryo begins, which enters the uterus on the 6th day after fertilization (21 days from the last cycle).

If this does not happen, then the pregnancy will not develop. An unfavorable scenario is possible - an ectopic pregnancy, when the embryo begins to develop in the tubes. Such a pregnancy cannot be saved Quite often, as a result of surgical intervention to eliminate it, the tube is destroyed and, as a result, problems with pregnancy are possible in the future.

After implantation into the uterus, the embryo continues its development, feeding through two blood vessels. The placenta begins to form around him. In addition, the unborn child constantly receives antibodies from the mother that protect it from various diseases during pregnancy.

At the end of the first month of pregnancy, the baby is like a bean, measuring 4 mm and weighing less than one gram. It is already possible to distinguish the future spine of the embryo. At this time, the heart of the unborn child begins to form, as well as:

• The heart and primitive circulatory system begin to form;
• Future arms and legs begin to appear;
• The umbilical cord is formed;
• You can guess the position of the future head.

Second month

During the second month of the child's development, eyes form over the weeks of pregnancy, and arms and legs begin to grow. Internal organs and brain develop, which leads to an increase in head size. At this moment, the fetus measures 3 cm and weighs about 3 grams and floats in a special bag in the amniotic fluid, which protects it from external shocks and impacts.

The face begins to form with the eyes, which are separated from each other and covered with a membrane, and the outlines of the ears also begin to appear. The lower part of the embryo is elongated and similar to a tadpole's tail, which disappears at the end of the second month. At the seventh week of embryo development, it is already possible to distinguish future fingers and toes.

At this time, the main internal organs begin to develop:

• intestines and stomach;
• bladder and urethra;
• liver;
• appendix and spleen;
• There is a slow development of bone and muscle tissue.

At this time, one of the most amazing events of the pregnancy process occurs: the small heart of the fetus begins to beat, and the frequency of its beating is equal to twice the frequency of the mother’s heartbeat and is 140-150 beats per minute.

Third month

From the third month of pregnancy, which covers from the 11th to the 14th week, the embryo is usually called a fetus, since it takes on a human form. At this time, the limbs of the unborn child develop very quickly, although the size of the head continues to be disproportioned relative to the rest of the body.

Starting from the 12th week, the fetus can open and close its mouth. These movements lead to the fact that he swallows amniotic fluid, which he then removes from his body through the urethra. Due to the development of muscle tissue, the baby’s first movements occur, which the expectant mother still does not feel.

Thanks to the development of nerve cells in the brain, the hearing aid begins to form. At this time, the fetus’s iris and cornea are already formed, and the eyes continue to be closed. Nails appear on the fingers and toes. The placenta has already acquired the round shape of the fetus. In some cases, ultrasound can reveal the sex of the baby.

A vital organ is also finally formed- the umbilical cord, consisting of two types of blood vessels:

• one vein;
• two arteries.

The vein is responsible for supplying oxygen and nutrient-rich blood to the fetus, while the arteries remove oxygen- and nutrient-poor blood from the fetus.

At the end of the first trimester of pregnancy, the baby measures 10 cm and weighs 50 grams. This is a small source of constant vibrations, which the expectant mother does not yet feel.

Second trimester

The amniotic fluid bag protects the baby from mechanical shocks and allows him some freedom of movement. At this time, the main features of the face and head have already been formed: eyebrows, nose and hair. The lips separate from the gums. The legs become much longer than the arms, and the number of nerve cells is equal to that of an adult.

The development of the fetus week by week leads at this stage to the fact that the child can already hear sounds that come from outside. Through the eye membranes, the child can perceive light and reacts to it when the woman's stomach is illuminated. The fetus begins to move its eyebrows and yawn. It is already clearly possible to distinguish. Starting from this stage, you can distinguish the child’s genitals and see whether it is a girl or a boy.

The fetus's intestines are filled with a green substance - the products of its vital activity, which will be removed from its body only after birth. The placenta, attached to the wall of the uterus, continues to grow and at the end of this month reaches one centimeter in thickness. If you press on the woman's stomach at this time, you can feel the baby's movements.

Fifth month

Between the 19th and 22nd weeks of pregnancy, the fetus already weighs more than the placenta. At this time, reflexes are formed. So, in addition to kicking his mother’s stomach, he begins to suck his finger. The movements become stronger, especially at night, and he is already able to somersault.

By the middle of this month, a child's brain is similar to that of an adult, as neurons are formed at a high rate during this time. A primitive immune system develops. In order to maintain body temperature, layers of adipose tissue begin to form. Baby teeth begin to form, the fetal heartbeat can be heard, nails continue to grow, eyebrows and eyelashes are already fully formed.

From this moment on, the child is able to distinguish the voice of his mother; he brings his head closer to the stomach if he likes external sounds, and moves it away from the stomach otherwise. Therefore, some experts recommend listening to classical music and talking to your child during this period to make him feel confident.

By the end of the month, the child already reaches 30 cm in length and gains a weight of 200-450 grams. The baby begins to sleep at regular intervals.

Sixth month

In the sixth month of pregnancy, the growth and movements of the fetus are very rapid. The first lines begin to appear on the palms. During this period, the skin of the fetus is wrinkled and red because the capillaries are transparent. He sleeps 18 to 20 hours a day, but when he wakes up (eyes still closed), he is very active. The child's hearing improves, and he can already distinguish his father's voice.

At the end of the second trimester, the baby's taste buds begin to develop, and he can distinguish between the sweet taste of amniotic fluid and other tastes, and begins to understand which ones he likes and which he doesn't. The intestines continue to fill with green substance, brain cells begin to mature, it is believed that at this time he can already learn and remember information. The alveoli of the lungs begin to grow, the diaphragm moves, and the bronchi remain filled with fluid.

At the end of the second trimester, the fetus measures 32 cm and weighs one kilogram. He has very little time left to learn to live independently of his mother’s body. If the baby is born at this point, it will need medical attention to survive.

Third trimester

From this moment, the bones of the fetus begin to harden, the skin remains transparent and wrinkled due to the presence of fatty layers under it. The brain becomes large enough, the nervous system allows the fetus to quickly learn and perform complex movements. Begins to navigate in space. So, if the fruit is already ripe and is preparing to be released into the world, it is positioned head down.

At the end of the seventh month, the unborn baby's heart rate increases every time his mother begins to speak. The fetus no longer has enough space; the volume of urine it produces is half a liter per day.

By the 28th week of pregnancy, he opens his eyes, however, only after birth his vision will become correct. At this time, he distinguishes only shadows. The sensitivity of the baby's body is such that it feels the mother's touch on the stomach.

Eighth month

Starting from the eighth month, the baby's skin becomes pink and soft, and the limbs become thick. At the end of the month, as a rule, the child is positioned head down, but before that he can still make small turns. His movements are less frequent due to the small space in the womb.

During this period, a large amount of fat accumulates under the skin. Often his head is covered with a lot of hair. He already has fairly developed vision and reacts to light changes outside. The iris of the eyes is blue.

The child can clearly perceive both low and high voices. Most organs are already formed with the exception of the lungs.

Ninth month

In the last month of pregnancy, the fetus's vision is fully developed, it is able to sense the dawn when the light of the sun hits the mother's belly. He rests his buttocks against his mother’s diaphragm, breathing movements occur more and more often, although there is still no air in his lungs.

The bones of the head have high plasticity to facilitate the birth of a child. At the end of this trimester, the fetus increases its weight by 28 grams per day. The nails have already grown a lot and in some cases newborns have scratches on their face.

The baby's intestines are full of a green substance that will begin to be excreted immediately after birth. By the last week of development, the fetus measures 45-55 cm and, due to lack of space, it is forced to bend strongly. Childbirth usually takes place 38-42 weeks after the start of pregnancy, when all the baby’s organs are working properly.

When planning a pregnancy, few people think how important it is to have information about a particular period of a pregnant woman’s life. Couples planning to conceive need to know how the fetus is formed in the first days of its life, in order, for example, to plan the gender of the child or to understand the need to prepare for pregnancy. We will try to consider in more detail the development of the embryo by day from conception to the end of the first trimester.

The development of an embryo from conception to birth is a rather complex period, the well-being of which is determined by the first days of intrauterine life. Fertilization plays a big role in determining the sex of the baby, and the subsequent stage at which the tissues and organs of the child are formed determines the success of the development of the fetus.

Any pregnancy begins from the middle of the menstrual cycle, namely from the moment of fertilization of the egg, although in obstetrics it is customary to consider the beginning of pregnancy the first day after menstruation. Conception occurs on the day of ovulation, since the ability of the egg to procreate is lost 12-24 hours after the rupture of the follicle.

In the fallopian tube, after the sperm penetrates the egg, a diploid cell is formed, which begins to divide exponentially. On the 4th day after conception, the zygote has 58 divided cells, 53 of which will become the basis for the formation of tissues and internal organs of the child, and the other 5 will take part in the formation of the placenta, amniotic sac and umbilical cord.

On day 5, the zygote enters the blastocyst stage, which is characterized by the presence of a bubble with liquid and subsequent resorption of the zygote membrane. At this stage, the embryo begins to gain weight. On days 7-10 after conception, implantation of the embryo into the uterus begins.

Attachment of the embryo to the uterus - the moment of truth

From conception to implantation, depending on various factors, 7-10 days pass. Implantation begins at the end of the week after conception, when the embryo, moving through the fallopian tubes, reaches the uterine cavity. Depending on the condition of the endometrium, its thickness and elasticity, the implantation process may take longer, in which case late implantation may be diagnosed. Normally, the process of fetal attachment takes about 40 hours. The thickness of the endometrium for attachment of the blastocyst should not be less than 7 mm.

From the first hours after the start of implantation, a woman’s body begins to produce a specific hormone, hCG, which sends a signal to the brain about the beginning of pregnancy. 9-10 days after the expected conception, a blood test for pregnancy can be performed. Implantation in 30% of cases can be accompanied by bloody discharge and, almost always, local nagging pain.

After implantation, the embryo continues to grow in the endometrium, which provides essential nutrients until the placenta forms.

10 days after conception, pregnancy occurs directly - the fetus has already established itself and is beginning to form. Immediately after attachment of the fetus, the embryo consists of three layers of cells from which the skin, internal organs and musculoskeletal system are formed. On days 14-20 after fertilization, the rudiments of the umbilical cord and placenta appear. During these days, the primary circulatory system and amniotic sac are formed, the number of cells increases, and the formation of all systems and organs of the child begins.

From 18 to 21 days after conception, the embryo’s heart begins to beat, which can be easily monitored using ultrasound; in parallel, on days 20-22, the baby’s skeleton is formed - the notochord, spinal cord, brain and its parts. On days 24-26, the foundation of the central nervous system is laid.

At 3 weeks after conception, from days 21 to 30, the baby’s limbs, neural tube and visceral arches form. By the end of 1 month, the baby’s muscle tissue, rudiments of eyeballs, and spine are clearly visible. Further growth of the embryo involves the development of existing rudiments.

From the 5th week, the embryo enters the fetal stage.

At 5 weeks from the moment of conception, the baby continues to develop all systems and organs, especially the brain. The child's primary sexual characteristics begin to appear. Continues

From the 6th week after conception, the baby develops ears, nose, eyes, eyelids, fingers and toes. The heart divides into chambers, and the kidneys and ureters form.

1st trimester screening

At week 7, the umbilical cord and placenta continue to form, through which the fetus is provided with air and food. By that time, the brain has a clear demarcation of the hemispheres, the formation of the child’s fingers and palms is completed, the eyelids and eyes are already formed. The endocrine system is launched.

At week 8, the fetus develops taste buds and the gastrointestinal tract and oral cavity are formed. The contours of the face are improved, and in boys, testicles are formed. The child's body begins to lengthen and the bones harden. By this time, the length of the embryo is 20 mm.

At the 9th week, the baby’s adrenal glands begin to produce hormones, the circulatory system continues to form, and in boys the prostate gland forms. There are red blood cells in the blood at this stage, although there are still no white blood cells. The baby's joints and muscular system are already formed, so the fingers, knees and elbows can already shrink. The formation of organs at this stage stops; all the efforts of the pregnant woman and the baby are aimed at further improving the systems.

At the 10th week after conception, the first trimester ends. This period in obstetrics is equal to 12 weeks of pregnancy, since the countdown begins from the first day of the last menstruation. The first screening is recommended to be carried out from the first day of the 10th week until the 6th day of the 13th week of pregnancy in order to identify possible malformations and determine the exact gestation period. The most accurate results are obtained by screening at 11-12 weeks.

As part of the first of two mandatory examinations, a pregnant woman must donate blood for hormone levels, Rh conflict, infections and undergo an ultrasound. An ultrasound examination evaluates the length of the fetus and the size of the head, the symmetry of the development of the cerebral hemispheres, the condition of the internal organs, the size of the bones, the size of the heart and tummy. During the examination, the doctor will be able to discern and prevent the development of pathologies.

Bottom line

The development of a child from conception to birth is a rather complex and labor-intensive process. The first trimester is the most important period of gestation, since at this time all the baby’s systems are laid and formed. At the end of the first trimester, a study is carried out that helps to track the correspondence of embryo development to the gestation period and prevent pathologies. For the expectant mother, screening is an opportunity to see the baby for the first time.

The first abdominal image is one of the most touching moments of pregnancy, what do you think?

Pregnancy is a physiological process in which a fertilized egg, first called an embryo and later called a fetus, develops in the uterus. The duration of pregnancy is about 9 astronomical or 10 obstetric months. Traditionally, the development of pregnancy is considered by trimesters. However, knowing how the embryo develops week by week is also of interest.

Embryo or fetus?

In medical science, you can often find two concepts related to the period of gestation - “embryo” and “fetus”. What's the difference between them?

Intrauterine development of the fetus is conventionally divided into two stages:

1. Embryonic – lasts the first eight weeks. At this time, the embryo that develops in the uterus is called an embryo.
2. Fetal (from 9 weeks until the moment of birth). At this stage, the fetus resides in the mother's womb.

How the child, his internal organs, systems, will develop during various periods of intrauterine development of the fetus is determined by the genetic code that was transmitted by the germ cells of the mother and father.

1-10 weeks

1 Week

Speaking about the first week of pregnancy, you should clearly understand what exactly is taken as the starting point. If we talk about obstetric weeks (regardless of whether there is a multiple pregnancy or not), then we take into account the first day of the last menstruation of the cycle when the woman had unprotected intercourse and, accordingly, conception occurred.

Sometimes the moment when contact occurred without the use of contraceptives is taken into account. By counting by days, you get the third obstetric week. If we take into account the date of the start of the delay in menstruation, we get the fifth. In gynecology, when analyzing the intrauterine development of the fetus by week, they often focus on obstetric timing.

The first few days, even if it is a multiple pregnancy, are not characterized by any clear signs. This time is the beginning of the menstrual cycle. The level of hCG (human chorionic gonadotropin) is within normal limits (5 IU/ml for non-pregnant women).

HCG fluctuations at the first stage are evidence of:

• previous abortion or miscarriage;
• taking hormonal drugs.

2 week

This time is marked by the fact that the zygote continues to mature in the uterus or fallopian tube, which, under favorable circumstances, will become a developing pregnancy.

Towards the end of this period, there comes a time when, after conception, the egg attaches to the wall of the uterus.

This can be indicated by discharge that is similar in consistency to egg white and even bloody. A slight discharge of blood is relative evidence of the attachment of an egg to the wall of the uterus and the appearance of an embryo. Heavy discharge during this period of pregnancy is not the norm.

3 week

It was at this time that it can be argued that conception occurred. The fruit is extremely small, its size is 0.15-0.2 mm in length, and its weight is only 2-3 mcg. If fertilization does not occur, the woman may begin her period several days earlier. When maintaining a special calendar, it is easy to notice a slight shift.

If the pregnancy was planned, significant bleeding may indicate a threat of miscarriage.

4 week

The embryo develops so actively that a woman may begin to feel the first signs of her changed status, especially if the pregnancy is multiple. There is swelling of the mammary glands, the nipples become sensitive. Menstruation is delayed, and scanty bleeding is sometimes observed.

At this time, there is an increased risk of fetal developmental abnormalities due to excessive physical activity, an infectious disease accompanied by high fever, and abuse of alcoholic beverages.

HCG levels only increase in the blood. On an ultrasound, you can see the corpus luteum, which provides nutrition to the embryo before the placenta begins to fully function, and is also involved in the production of progesterone, the so-called pregnancy hormone.

The size of the embryo increases. It is already 5 mm in length.

The fruit weighs 3.5 g and length is from 4 to 7 mm. The rudiments of limbs, fingers, eyes, ears, slits for the nose and mouth, and some glands and systems begin to form. The size of the uterus changes.

An ultrasound specialist at this time can tell whether a woman is developing a multiple pregnancy or whether she will have one child. During the examination, the diameter of the amniotic sac is determined, as well as the coccygeal-parietal size and the “growth” of the fetus. The last digit will appear in the results throughout the first trimester.

Changes in the body become more noticeable. Some women note a slight increase in body temperature to subfebrile levels. However, if the condition begins to fit the description of a cold, you should immediately consult a doctor.

6 week

The woman begins to show signs of future motherhood. The uterus reaches the size of a plum - an experienced gynecologist is able to feel it during the examination. If there is a multiple pregnancy, an ultrasound will show two fetal and yolk sacs. The examination will also allow you to see small tubercles - here, over time, the upper and lower limbs will appear, and you can also hear the heartbeat using a special device. Facial features gradually emerge. The embryo reaches a length of 4-9 mm, its weight is no more than 4.5 g.

week 7

The fetal heart becomes four-chambered and large blood vessels are formed. The first trimester is marked by the continued development of all internal organs and systems. Weight – 1 g, coccygeal-parietal size is 13 mm. The unborn child gradually begins to straighten up. The brain is developing rapidly.

The face and upper limbs are improved. The umbilical cord completes its formation and a mucous plug forms.

The size of the fruit increases significantly - 14-20 mm in length, it begins to move. By the middle of the first trimester, the face acquires more and more human features. The formation of organs and systems has been completed, some of them are actively functioning. The optic nerve is born, the rudiments of the genital organs appear.

Week 9

The coccyx-parietal size of the unborn child reaches 22-30 mm, weight - 2 g. The cerebellum, pituitary gland, middle layer of the adrenal glands, lymph nodes, and genitals are actively formed. The functioning of the cardiac and nervous systems is improved. The upper and lower limbs begin to move, bend, and muscles appear. The fetus gains the ability to urinate.

The critical first stage of development ends for the fetus. Weight reaches 5 g, and height – 30-40 mm. The heart rate reaches 150 beats per minute. The limbs are fully formed, you can see the joints and fingers. The foundation of baby teeth is laid, which obliges the mother to keep a food calendar and mark the consumption of dairy products in it. Most of the gastrointestinal tract organs have already completed their formation.

11-20 weeks

11 week

The critical stage of development is virtually over. The weight of the fetus reaches 8 g, the “height” is 5 cm. From this moment, the embryo enters the fetal stage. The heart is working fully, the formation of blood vessels is completed. The placenta becomes dense. The liver occupies 10% of the body. The intestines make the first movements similar to peristalsis.

The genital organs are increasingly formed. Eye color is determined and the sense of smell appears. Palms and fingers become sensitive.

12 week

Critical moments for fetal development depend more on the health and lifestyle of the mother. The body length ranges from 6-9 cm. The unborn child already has fingers and nails are forming. The gastrointestinal tract organs are completing their formation. The immune system is improved.

The first trimester ends, the critical cycle is completed. The baby teeth are fully formed, muscle and bone tissue continues to form, and the digestive system develops. The genital organs are differentiated. The child’s “height” reaches 8 cm, weight – 15-25 g.

Week 14

The baby is actively growing and developing. Its weight is 30-40 g, and its height is from 8 to 10 cm. The resemblance to a person is increasing. In case of multiple pregnancy, the expectant mother can feel the movements of the children, who are becoming more and more active.

The bone skeleton grows, ribs are formed. The movements of the diaphragm resemble breathing. All organs and systems are fully formed. The child has an Rh factor and blood type.

Starting from the 15th week, the baby’s cerebral cortex begins to form. The process will take most of the second trimester. The endocrine system, sebaceous and sweat glands are activated.

Taste buds are fully formed, breathing movements are improved. The baby’s weight reaches 70 g, from the tailbone to the crown it is already as much as 10 cm. But even with multiple pregnancies, this does not interfere with free movements.

Week 16

By the first half of the second trimester, the baby is already 11 cm tall and weighs 120 g. The neck has taken an even position, the head rotates freely. The ears and eyes gradually rise upward. The liver takes over digestive functions. The development calendar is becoming busier. The composition of the blood is completely formed. The immune system turns on, interferon and immunoglobulin are produced. The baby is able to protect itself from infections coming from the mother.

But they all continue to be critical for the small organism. The fetus develops a layer of fat. If a girl grows, by the middle of the second trimester she will have a uterus. A person's height is 13 cm, weight is 140 g. He is able to hear sounds from the outside and feel emotions. From the point of view of emotional and mental development, week 17 is critical - establishing contact is extremely important.

The second trimester is approaching the middle. The upper and lower limbs of the fetus, phalanges of the fingers, and prints on them are fully formed. Fat tissue, the immune system and the brain continue to actively develop at week 18. The rudiments of molars are formed.

A reaction to light appears, and hearing increases. The calendar must include the date of the first movements and their frequency. Fetal height is 14 cm, weight – 200 g.

There is a big leap in development. Movements become more orderly. The respiratory system is improving. The body is covered with vernix. By week 19, the head rotates freely and is held in one position. Weight reaches 250 g, and height – 15 cm.

The child is already fully formed, his organs are improving. By week 20, the heartbeat can be heard with a regular stethoscope. The limbs are fully formed. The sensations of sounds become more acute. The length is 25 cm, and the weight is about 340 g. The movements are more noticeable for the mother.

21-30 weeks

By 21 weeks, the baby gains height - 26.7 cm and weight - 360 g. But there is enough room for active movements. The digestive system works more actively, the fetus constantly swallows amniotic fluid. Muscle and bone tissue are strengthened. The spleen is involved in the work of the body.

Week 22

The period is marked by a significant increase in weight - up to 500 g. Height also changes - as much as 28 cm. The fetus at these times is viable even if it is first born. The brain and spine are fully formed. Reflexes are improved. The heart increases in size.

Week 23

By the 23rd week the fetus is sufficiently formed, the digestive system is fully functioning. Adipose tissue accumulates. The genital organs are clearly differentiated.

The baby's height reaches 29 cm, and his weight is 500 g. The spleen becomes more active.

Externally, the fetus already looks like a child. Due to the small amount of adipose tissue, the weight is only 600 g with a height of 30 cm. By week 24, independent production of growth hormone begins.

The respiratory system enters the final stage of development. Reflexes and sensory organs are improved. A sleep and wakefulness pattern is developed. The baby begins to listen to the mother’s emotions. The movements become sensitive.

The fetus gained weight to 700 g and grew to 34.5 cm. The resemblance to a newborn increases.

The lungs are preparing for the first independent breath. The hematopoietic function is completely carried out by the bone marrow.

The sense of smell is highly developed, the child senses the mother’s mood swings. The bone skeleton is actively overgrown with muscles. Testicles and vagina appear.

The fruit acquires individuality. The eyes begin to open. The child is able to recognize the voice of his mother and father. Bone tissue is strengthened. The lungs are finally taking shape. The brain produces various hormones. The baby weighs 750 g, he is as much as 36.5 cm long. He sleeps 16-20 hours. Movements can be noticed by others.

Week 27

The fetus weighs 900 g by 27 weeks. Growth becomes more active. The endocrine system also enters a new phase of activity. The stability of a child’s pancreas determines the development of metabolic processes and mental abilities. The production of surfactant, a substance that allows the lungs to open after birth, stabilizes.

The amount of subcutaneous fat increases. The mother feels the baby’s training even more strongly.

Bone tissue continues to strengthen. Alveoli appear. The future little man can weigh 1 kg or more. Having reached 38.5 cm in height, the baby begins to feel a lack of free space in the uterine cavity, although this does not in any way affect his activity.

Week 29

The baby's body is gradually preparing for the upcoming birth. Thermal regulation and the functioning of the immune system are improved. The blood composition has been stabilized. The digestive system is completely ready to digest food. The gaze begins to focus. The skin gradually brightens and loses wrinkles. Subcutaneous fat increases, muscle tissue strengthens.

Week 30

The child’s weight reaches 1500 g. Gradually the nervous system “turns on.” The liver accumulates iron. The work of the heart acquires sexual differentiation - in boys it beats more calmly than in girls. Typically, by this time the fetus is in the position from which it will be born. Movements become calmer. Eyes open.

31-40 weeks

The child may already weigh more than 1.5 kg. The liver acquires the ability to cleanse the blood.

Surfactant production continues. The connection between peripheral nerve cells and the brain is established. Having touched the cornea, the baby will definitely close his eyes. The calendar of intrauterine development is gradually ending.

32 week

The active growth phase continues. Organs and systems are fully functioning. The skin and appearance take on a familiar appearance. Lanugo, the original down, gradually disappears.

The baby is finally in position for birth. The skull remains soft.

At this time, the weight reaches 2000 g. Muscles and subcutaneous fat continue to build. Body parts become more proportional, many body systems work fully. The child is able to express emotions. The kidneys are prepared for their main function - filtration.

34 week

Fetal development is coming to an end. Individual traits become more and more obvious. Gastrointestinal tract training is more active.

By these days, organs practically do not develop. Activity is observed in terms of building muscle and fat tissue. Every week the baby gains up to 220 g. The skin is deprived of lanugo and completely smoothed out. Shoulders are rounded.

The body continues to improve. Iron continues to accumulate in the liver, and vital systems are being adjusted. The baby actively sucks his thumb in preparation for the upcoming breastfeeding. Most children occupy, that is, head down.

Week 37

The fruit is fully formed. The gastrointestinal tract is ready to receive and digest food, peristalsis is activated. Heat exchange processes have been established. The lungs are ripe. Iron accumulates in the liver. Height and weight increase weekly.

The baby is ready to be born. In male children, the testicles descend into the scrotum. The skin takes on a pink tint.

The fetus is fully formed, its organs and systems are ready for independent functioning. Reaction to sounds and light is developed. There is no original lubricant on the surface of the skin.

Week 40

The baby's height is approximately 54 cm, weight - from 3 to 3.5 kg. The formation is completely completed.

Knowledge of how the child develops at each stage of the gestation period will allow the mother to better respond to the changes occurring in her body. This is also of greater importance for the observing gynecologist - he will be able to respond to pathological abnormalities in a timely manner.

The human life cycle is a series of victories and defeats, joys and sorrows. And one of the most important achievements is the birth of a child. This is the moment when a person, overwhelmed with happy emotions, begins to feel significant and needed. Children are the flowers of life, who bring their own piece into the comfortable life of their parents and make them relive the memories of their childhood.

The life of a baby begins from the moment of conception, and, of course, it is very important for future parents to monitor how the child’s intrauterine development occurs. The entire pregnancy consists of 40 weeks and is divided into 3 stages.

Stages of development

The stages of intrauterine development of a child in obstetric practice are usually called trimesters. This is a kind of division of the entire pregnancy into three equal periods, according to which the vital functions of the fetus are assessed, tests and ultrasound are prescribed, and the pregnant woman is measured. The appearance of any physiological and psycho-emotional changes in the body of the expectant mother is typical for a certain trimester, and if they are not pathological, then they are considered the norm.

I trimester

It starts at 1 week and ends at 13. It is considered the most dangerous, since it is at this time that the fertilized egg attaches to the wall of the uterus; if this does not happen, pregnancy does not occur.

Also at this time, the rudiments of future organs and tissues begin to form, so it is very important during this period to monitor your diet, rest on time and spend more time in the fresh air. At this stage, a woman may experience such an unpleasant symptom as toxicosis. There is nothing wrong with this, unless it is very pronounced and protracted, in which case it is best to consult a doctor. Some women may experience the following changes in the first trimester:

• disturbance of taste perception of food;
• frequent mood changes;
• the appearance of drowsiness and headaches.

All this is often associated with changes in hormonal levels and the beginning of the body’s preparation for bearing and giving birth to a child.

II trimester

It starts at week 14 and ends at week 26. This trimester is characterized as the calmest and most pleasant period of pregnancy. The child's intrauterine development continues, and at the same time new sensations appear - this, of course, is the baby's movements, which the expectant mother begins to clearly feel. In primiparous women this occurs at 18-24 weeks, and in multiparous women it can be noticed starting at 13, because they have already given birth before and know what it is.

III trimester

Starts at 27 weeks and ends with childbirth. The safest intrauterine period of child development, but at the same time very restless. The child is already almost formed and in case of premature birth is ready for independent existence. A pregnant woman begins to develop a feeling of anxiety and fear, the baby’s frequent movements are more distinct, and at some moments you can even notice how the stomach “shakes.” Unpleasant symptoms such as heartburn and shortness of breath appear due to the pressure of the enlarged uterus on the stomach and diaphragm.

The physiological process of child development is usually divided into 3 periods:

Ultrasound during pregnancy

Currently, ultrasound examination is necessary to evaluate

fetal life and detection of congenital defects. In total, this procedure must be completed 3-4 times during the entire period of pregnancy. The first time at 12 weeks, the second at 21-24, the third time at 32 weeks. During this procedure the following is assessed:

• intrauterine development of the child;
• compliance with the gestational age;
• baby's weight and height;
• its position in the uterine cavity;
• the presence of congenital defects;
• is there an umbilical cord entanglement;
• the condition of the placenta and amniotic fluid, as well as their quantity.

During pregnancy, no special changes are observed in a woman’s body. During this period, the egg is fertilized by a sperm and a zygote is formed, which will actively divide and go into the uterine cavity.

2 month. The intrauterine development of a child in the second month is characterized by the fact that the baby is already developing legs and arms, and fingers on them. All internal systems develop and the heart begins to beat at a frequency of 140-150 beats per minute. The weight of the fetus is 4-5 grams, and the height is 2.4-3 cm.

3 month. This month ends. The child's development continues, and at the same time, vocal cords, tongue, hair and nails begin to form. The first rudiments of teeth appear in the oral cavity. The digestive and circulatory systems begin their work.

4 month. During this period, the baby becomes larger. All his organs and systems are actively working, and the child himself already knows how to bend and straighten his limbs and push with his legs. Special changes include the development of the cerebral cortex, ears and the appearance of an individual pattern on the tips of small fingers, and the baby also becomes sensitive to external sounds.

5 month. All systems and organs continue to improve. If we talk about the intrauterine development of a child by month, then the fifth month is perhaps the most memorable for a first-time pregnant woman. At this stage, she can feel and feel the baby inside her. The lungs are still underdeveloped, so you should take better care of your health to avoid premature birth.

6 month. This month of pregnancy brings with it many changes in the development of the fetus. By this time, he had learned to open and close his eyes, on which eyelashes appeared and eyebrows on top. The genitals are formed, and individual features can be seen on the face. At this stage the baby weighs 750g and is approximately 30cm tall.

7 month. During this period, the brain and lungs develop rapidly. There is more and more subcutaneous fat, so the skin becomes smoother and fewer wrinkles remain on it. The baby's height this month is 33 cm, and his weight is about 1-1.2 kg.

8 month. During this period, the child significantly gains weight and increases in height. His skin is covered with thick hair, and the fat layer has become even larger. The baby begins to react violently to all external stimuli.

9 month. The final stage of the entire pregnancy. By this time the child is fully formed and ready for independent existence. The lanugo (fluff) on his skin completely disappeared, and it became smooth and pink.

During all periods of the child’s intrauterine development, one should adhere to

A few rules and tips:

• Review your diet and, if necessary, add vitamin-rich foods to it.
• Do not overwork, sleep and rest are important for the full development of the child.
• At the beginning of pregnancy, you should start taking folic acid, naturally, under the supervision of a doctor. Do not use other drugs unless prescribed.
• If you have bad habits (alcohol, smoking), you should give them up, because... They do not have a positive effect, rather the opposite.
• Walk in the fresh air more often, but under no circumstances overcool.
• Sexual life with a partner can be continued if there are no contraindications.
• Buy a prenatal and postnatal bandage, it will be very useful.
• Clothes should be loose and not restrictive; shoes should be low-heeled.

Pregnancy is a very important period in the life of a woman and her significant other, so it’s worth remembering every moment of this wonderful time and just enjoying it.