Uterine changes during pregnancy

The development of the human body in the first 9 months takes place in an amazing maternal organ - the uterus. A fertilized egg, moving along the fallopian tube, enters the prepared uterine cavity and remains in it for a long 40 weeks. On average, this is how long a normal pregnancy lasts. A small person grows out of a tiny cell, changing the shape, density and volume of the uterus during pregnancy.

How is the uterus?

The uterus is a hollow, unpaired muscular organ of a pear-shaped form. During the gestation, the size of the uterus grows several times, the walls stretch, and after childbirth it returns to a size slightly larger than the previous one.

It is located in the abdominal cavity between the bladder and the lower part of the colon. Anatomically, the bottom, body and neck are secreted in the uterus. The part between the cervix and the uterus is called the isthmus.

• The bottom is the upper part of the uterus.
• The body is the middle, most voluminous part of the organ.
• The cervix is ​​the narrowest part of the uterus that ends in the vagina.

The weight of the uterus of a healthy nulliparous woman is only 40-60 g. After birth, it increases to 100 g as a result of tissue hypertrophy. The length of the uterus can reach 7-8 cm with a width of 4-6 cm, and the average thickness is 4.5 cm. The body volume of the uterus is approximately 5 cm³. The uterus is a relatively mobile organ held by muscles and ligaments. Its location may vary relative to surrounding organs. This may be the orientation along the straight axis of the pelvis, the position, inclined forward and tilted back.

The walls of the uterus consist of 3 layers: serous (perimetry), muscle (myometrium) and mucous (endometrium). The condition of the endometrium depends on the day of the menstrual cycle. If pregnancy occurs, then it thickens and supplies the fetal egg with all the necessary substances in the first months of development. Otherwise, the uterine mucosa is rejected and exits during menstruation. So the endometrium is updated. The myometrium is responsible for the increase in the uterus. In the first half of pregnancy, new muscle fibers are actively formed in this layer, existing ones are lengthened and thickened. The wall thickness during this period is approximately 3.5 cm. After 5 months of pregnancy, the uterus grows exclusively under the influence of stretched and thinning walls. And closer to the birth, the walls of the uterus become very thin, about 1 cm thick. Therefore, it is so important that pregnancy occurs after a sufficient time after gynecological operations on the uterus or a caesarean section. A scar on the uterus can be insolvent during the period of growth of the uterus and during childbirth, which will lead to tragic consequences.

The role of the uterus in the female reproductive sphere

The main task of this body is to raise a new person, and then release him into the world. The uterus during pregnancy increases several times due to the elastic muscle layer. Under the influence of the growing body of the child, its form from pear-shaped turns into an egg-shaped. And during childbirth, rhythmic uterine contractions (contractions) help the baby to be born.

Stages of uterine change during pregnancy

Preparation for pregnancy takes place in the uterus before conception. During each menstrual cycle, in its luteal phase, the functions of the endometrium change, and the uterus becomes ready to accept a fertilized egg for implantation.

First trimester

A few days after the sperm meets the female cell that occurs in the fallopian tube, the dividing egg enters the uterus. Then implantation of the embryo into the uterine wall begins and fixation in it. The uterine wall thus becomes thicker. But during this period, uterine growth associated with pregnancy can be assumed only after an ultrasound scan. At the beginning of growth, the uterus during pregnancy becomes spherical. And only a little later increases in the transverse size. The uterine wall during pregnancy in the early stages swells and softens. A rounded bulge appears on its surface at the site of implantation of the embryo. But the uterus is still located behind the pubic symphysis and is not accessible for palpation, although its body has already increased almost 2 times. Gradually, the ovum grows, occupies the entire uterus and the asymmetry goes away. By the end of the third month, the bottom of the uterus reaches the upper border of the pubic joint. And in size, the uterus resembles an average grapefruit, and compared with the beginning of pregnancy, it increases by 4 times. The upper part of the uterus can already be palpated through the abdominal wall.

Second trimester

From about the 20th week of pregnancy, the expectant mother may begin to feel training contractions. These are short, rhythmic, irregular contractions of the uterine muscles, which are absolutely safe and are not a sign of the onset of labor. A woman experiences tension in the abdomen and sacrum, and with her hands on her stomach, she can feel the fight tactilely. There are several options for the causes of the precursor contractions and their role in preparing for childbirth. Some doctors believe that contractions prepare the female body for the upcoming birth: they stimulate the maturation of the cervix and train the muscles of the uterus. This is where their name came from. Others think that these contractions increase the uteroplacental blood flow and are the result of changes in the hormonal balance in the pregnant woman's body. At this time, the size of the uterus continues to gradually increase.

Third trimester

At 8 months of pregnancy, the upper borders of the uterus reach the costal arch. A highly located uterus presses on the nearest organs and diaphragm, complicating the free breathing of the expectant mother. At the end of 9 months of pregnancy, the uterus has approximate dimensions: length - 38 cm, thickness - 24 cm, and transverse size - 26 cm. Its net weight is 1000-1200 g. The total volume of the uterus before birth begins to grow 500 times compared with non-pregnant condition. In the final month of pregnancy, the bottom of the uterus returns to the height of the eighth month of gestation. The baby's head may begin to sink into the birth canal.

After the end of childbirth - the birth of the baby and the placenta - the uterus begins to contract rapidly. And by the 2nd day after birth, its bottom is located in the middle of the abdomen. A further decrease in the size of the uterus is gradual, an average of 1-2 cm per day. Breastfeeding helps the uterus contract faster and restore its previous state. In this regard, when feeding the baby in the early days, the mother may feel pain in the lower abdomen, similar to contractions.

Uterine tone

At a doctor’s appointment during an external obstetric examination, the doctor assesses the tone of the uterus during pregnancy. With increased tone, usually the soft wall of the body hardens. Also, the tone is diagnosed with an ultrasound examination of the uterus.

Uterine hypertonicity during pregnancy is one of the signs of the threat of spontaneous interruption of the gestation process. Serious threat. It can appear at any month of pregnancy. Symptoms of uterine tone during pregnancy are considered to be pulling pains of different strengths in the lower back and lower abdomen. Pain syndrome depends on individual sensitivity, the level of intensity of uterine hypertonicity and its duration. Short-term and short-term uterine tone during pregnancy without spotting can be caused by the growth of the uterus, physical and emotional stress. This condition does not need to be treated, but it requires a change in the woman’s lifestyle to a more measured one. In any case, it is worth telling the doctor who is observing pregnancy about all the unusual, disturbing sensations.

If a pregnant woman has disturbing sensations in the lower abdomen resembling pain during menstruation, then a woman can independently assess whether the uterus is in good shape or not. To do this, lie with your back on a flat surface, relax and carefully feel your stomach. It should be relatively soft. If the stomach is tense and firm, then, probably, the uterus is now in good shape.

How does the cervix change?

The uterine neck is a dense but elastic muscular organ. In a non-pregnant woman, her length is about 4 cm. During an internal examination, the doctor observes the vaginal part of the neck - the external pharynx. If a woman did not give birth, then it is closed. But after giving birth, the pharynx may remain slightly ajar.

The cervix at the beginning of pregnancy is closed and long. It has a dense structure and is deep in the vagina. One of the first signs of a pregnancy is the changed color of the neck: a bluish tint appears in the pink, natural color for it. Normally, the cervix during pregnancy has a length of more than 3.5 cm and a strong structure. Her external pharynx is closed or may miss the tip of the finger in women giving birth. The size of the neck and its density are important diagnostic criteria when examining a pregnant woman. Their indicators may indicate the quality of the course of pregnancy and the potential risk of the onset of premature labor. For example, according to the results of the examination (manual and using an ultrasound device), the doctor determines the level of maturity of the neck. She can be immature, ripening and mature. To accurately assess this indicator, the gynecologist takes into account the position, consistency and length of the organ.

Changes in the cervix by weeks of pregnancy are most often diagnosed by a gynecologist after 5 months of gestation. But earlier verification procedures related to the individual characteristics of the course of pregnancy may also be carried out. So, the normal indicator of the neck length from the 10th to the 29th week is 3-4.5 cm. Then the neck begins to gradually shorten. And by the 32nd week, the indicator of its length along the upper border of the norm is reduced to 3.5 cm. With multiple pregnancy, the length of the uterine neck is also estimated, although the burden on the body of the expectant mother is increased and the risk of starting childbirth before the 38th week is great.

The cervix is ​​considered long if its size is more than 3.5 cm. This length is a positive prognostic sign of the onset of labor after 34 weeks of pregnancy. The cervix less than 3.5 cm in length indicates less positive prognoses. However, a woman can still be relatively calm. Such a neck is called short. The uterus during pregnancy with a neck of less than 2 cm is diagnosed as pathological. A pregnant woman is diagnosed with isthmic-cervical insufficiency. This is a serious condition that threatens the natural course of pregnancy. It requires maximum rest for a woman, and can be partially corrected by correctly selected therapy by a treating gynecologist. A short neck during pregnancy for up to 37 weeks is a serious sign that requires careful medical supervision. Shortening the neck increases the risk of premature birth in the third trimester or spontaneous abortion in the early stages.

Performing its main task - preserving pregnancy, the neck should be long and dense until the very birth. At the end of pregnancy, its active physiological maturation occurs. About 2 weeks before the birth, it softens and contracts to about 1 cm. The internal pharynx opens, and in childbirth it expands to 10 cm. After the birth of the baby, the neck gradually returns to its previous state.

What does a woman feel?

Usually, the uterus grows imperceptibly and painlessly for a pregnant woman. Like all biological processes, changes in the uterus during pregnancy occur in stages and without sudden jumps. Sometimes in the first months of pregnancy, the expectant mother may feel unusual sensations in the growing uterus. Most often, they are associated with the restructuring of the structure of the ligaments that support the organ. In special cases associated with pathological processes in the abdominal cavity or chronic diseases, a pregnant woman may experience pain. It is worth remembering that if any unusual or painful sensations appear, you must urgently seek medical help.

The uterus during pregnancy: what kind of examinations does the doctor conduct?

There are several mandatory medical procedures and procedures through which every woman who is observed by a doctor during pregnancy passes through. They are relatively simple and safe. As a result of their conduct, the doctor receives information about the condition of the uterus and the baby.

Until about 6 weeks of pregnancy, changes in the uterus are insignificant, and examination by a doctor to diagnose her condition is not of practical use. To diagnose pregnancy after a two-week delay of menstruation, it is recommended to do an ultrasound examination of the uterus. Using a transvaginal sensor, the doctor will be able to determine the level of pregnancy, its features and even see the heartbeat of the embryo. A qualified doctor at this time can already determine the increase in the uterus by palpation and make an assumption regarding the duration of pregnancy.

Also, to obtain data on the size, position and density of the uterus in the first trimester, the gynecologist conducts a manual (bimanual) examination of the organ. To do this, he places two fingers of his right hand in the vagina of a pregnant woman, and with his left hand he gently palpates the front abdominal wall, moving towards the fingers of the opposite hand. So the doctor finds the uterus and evaluates its current characteristics. It is important to know that too frequent gynecological examinations can provoke contractions of the uterine myometrium and increase the risk of abortion. It is especially worthwhile to refrain from such manipulations with diagnosed isthmic-cervical insufficiency, which leads to critically early opening of the cervix.

From the 4th month of pregnancy, the observing doctor begins to apply the techniques of Leopold-Levitsky: 4 methods of external obstetric examination of the fetus through the abdominal wall. They help determine the presentation, position and position of the baby in the uterus. These manual measurements are carried out very carefully so as not to increase the tone of the uterus and muscle tension of the abdominal wall.

The first method helps to find the highest edge of the uterus and determine which part of the baby’s body is located in this part of the organ. To do this, the doctor places both hands on the highest point of the uterus and, gently pressing, estimates its height and compliance with the month of pregnancy. It is also determined whether the head or pelvic end is at the bottom with the child's longitudinal position. The head has a dense and rounded shape, and the pelvic area is larger. It can move with the body of the child.

The second obstetric technique establishes the position of small parts of the child’s body - arms, legs, back. Also, this technique helps to assess the position of the child in the uterus, its tone and excitability. The doctor moves his hands to the mid-abdomen of the pregnant woman and gently, alternately, feels the area under the palms. If the baby is in a longitudinal position, then on the one hand legs and arms are determined, and on the other - the back.

Using the third method, the gynecologist evaluates the area of ​​the child’s body that is in the pelvis and will first pass through the birth canal. Another doctor determines the degree of omission of the preceding part. For this, the area above the symphysis is palpated. In this case, the head has clearer boundaries than the pelvic end in the longitudinal position of the child.

The fourth method of palpation of the uterus is carried out in order to clarify the position of the precursor in relation to the entrance to the small pelvis. If a child’s head is presented, then it can be lowered into a small basin, located above its entrance or pressed against it. The obstetrician places his palms on the lower part of the uterus on both sides and gently feels the selected area.

Uterine fundal height

Measurement of the height of the uterine fundus (VDM) is a routine procedure performed by the obstetrician at each appointment. It is used, starting from 4 months of pregnancy, in order to clarify the growth rate of the uterus and establish its relation to the gestational age. To do this, the pregnant woman lies on her back and the doctor measures the space from the upper edge of the pubic joint to the highest point of the bottom of the uterus with a centimeter tape or tazomer. Before measuring a pregnant woman, it is necessary to empty the bladder. Otherwise, an incorrect value may be obtained. From the second trimester of pregnancy, the VDM value in centimeters is approximately equal to the gestational age in weeks.

During pregnancy, the height of the uterus is determined by many factors: multiplicity, position and size of the baby, the amount of amniotic fluid. Accordingly, with polyhydramnios or a large baby, the uterus increases in size more, and its bottom is higher. , .

The uterus is an unusual female organ that preserves and gives life to a new person. Changes in the uterus during pregnancy surprise and make you wonder how rationally and beautifully the human body is arranged.