Changes in the uterus during pregnancy

2024 Author: Priscilla Miln | [email protected]. Last modified: 2024-01-15 22:35

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

How is the uterus?

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

It is located in the abdominal cavity between the bladder and the lower part of the large intestine. Anatomically, the uterus is divided into the fundus, body and neck. The part between the cervix and the body of 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 body.
• The cervix is the narrowest part of the uterus that ends in the vagina.

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

The walls of the uterus consist of 3 layers: serous (perimetry), muscular (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 mucous layer of the uterus is torn off and comes out during menstruation. So the endometrium is updated. The myometrium is responsible for the enlargement of 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 the 5th month of pregnancy, the uterus grows solely under the influence of stretching and thinning walls. And closer to childbirth, 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 may fail during the growth of the uterus and during childbirth, which will lead to tragic consequences.

The role of the uterus in the female reproductive system

The main task of this body is to raise a new person, andthen release it to 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 shape turns from pear-shaped to 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 meeting of the sperm cell with the female cell, which occurs in the fallopian tube, the dividing egg enters the uterus. Then the implantation of the embryo into the wall of the uterus begins and fixation in it. The wall of the uterus becomes thicker. But during this period, the growth of the uterus associated with pregnancy can only be assumed after an ultrasound examination. At the beginning of growth, the uterus becomes spherical during pregnancy. And only a little later it increases in transverse size. The wall of the uterus during pregnancy in the early stages swells and softens. A rounded bulge appears on its surface at the site of embryo implantation. But the uterus is still located behind the pubic symphysis and is not accessible for palpation, although its body has already increased by almost 2 times. Gradually, the fetal egg grows, occupies the entire uterus and the asymmetry disappears. Tothe end of the third month, the bottom of the uterus reaches the upper border of the pubic articulation. And in size, the uterus resembles an average grapefruit, and compared to the beginning of pregnancy, it increases 4 times. The upper part of the uterus can already be palpated through the abdominal wall.

Second trimester

At about the 20th week of pregnancy, the expectant mother may begin to feel exercise 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 by placing her palms on her stomach, she can feel the contraction tactilely. There are several options for the causes of contractions-harbingers 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 uteroplacental blood flow and are the result of changes in the hormonal balance in the body of a pregnant woman. At this time, the size of the uterus continues to gradually increase.

Third trimester

At the 8th month of pregnancy, the upper borders of the uterus reach the costal arch. The high position of the uterus puts pressure on the nearest organs and the diaphragm, making it difficult for the expectant mother to breathe freely. At the end of the 9th month 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 beforethe onset of labor increases 500 times compared with the non-pregnant state. In the final month of pregnancy, the fundus of the uterus returns to the height of the eighth month of gestation. The baby's head may begin to descend into the birth canal.

After the end of childbirth - the birth of the child and the placenta - the uterus begins to contract intensively. And by the 2nd day after childbirth, its bottom is located in the middle of the abdomen. Further reduction in the size of the uterus is gradual, on average by 1-2 cm per day. Breastfeeding helps the uterus contract faster and restore its former condition. In this regard, when feeding the baby in the first days, the mother may feel pain in the lower abdomen, similar to contractions.

Uterine tone

At a medical appointment during an external obstetric examination, the doctor assesses the tone of the uterus during pregnancy. With increased tone, the usually soft wall of the organ hardens. Also, the tone is diagnosed by ultrasound examination of the uterus.

Hypertonicity of the uterus 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 varying strength in the lower back and lower abdomen. The pain syndrome depends on individual sensitivity, the level of intensity of uterine hypertonicity and its duration. A short-term and short-term tone of the uterus during pregnancy without spotting can be caused by the growth of the body of the uterus, physical and emotional stress. This state is not needed.to treat, but it requires a change in the woman's lifestyle to a more measured one. In any case, any unusual, disturbing sensations should be reported to the doctor observing the pregnancy.

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

How does the cervix change?

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

The cervix at the beginning of pregnancy is closed and long. It has a dense structure and is located deep in the vagina. One of the first signs of the onset of pregnancy is the changed color of the cervix: 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 os is closed or may pass the tip of a finger in women who have given birth. The size of the cervix and its density are important diagnostic criteria when examining a pregnant woman. Their indicators can indicate the quality of the course of pregnancy and the potential risk of onsetpremature labor activity. For example, according to the results of the examination (manual and using an ultrasound machine), the doctor determines the level of maturity of the cervix. It can be immature, maturing 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 week of pregnancy are most often diagnosed by a gynecologist after 5 months of bearing a baby. But earlier screening procedures related to the individual characteristics of the course of pregnancy can also be carried out. So, the normal length of the neck 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 limit of the norm is reduced to 3.5 cm. In multiple pregnancies, the length of the uterine cervix is also estimated, although the burden on the body of the expectant mother is increased and the risk of labor beginning before the 38th week is high.

The cervix is considered long if its size is greater than 3.5 cm. This length is a positive prognostic sign of the onset of labor after 34 weeks of pregnancy. A cervix less than 3.5 cm in length indicates less positive prognosis. However, a woman can still be relatively calm. Such a neck is called short. The uterus during pregnancy with a neck 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 a well-chosentherapy by the attending gynecologist. A short neck during pregnancy for up to 37 weeks is a serious sign that requires careful medical supervision. Cervical shortening increases the risk of preterm labor in the third trimester or spontaneous abortion in the early stages.

Fulfilling its main task - the preservation of pregnancy, until the very birth, the neck should be long and dense. At the end of pregnancy, its active physiological maturation takes place. Approximately 2 weeks before delivery, it softens and shrinks to about 1 cm. The internal os opens slightly, and during childbirth it expands to 10 cm. After the birth of the baby, the cervix gradually returns to its previous state.

How 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 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 you experience any unusual or painful sensations, you should urgently seek medical help.

Uterus during pregnancy: what examinations does the doctor perform?

There are several mandatory medical manipulations and procedures that everya woman seeing a doctor during pregnancy. They are relatively simple and safe. As a result of their conduct, the doctor receives information about the condition of the uterus and the child.

Up to about 6 weeks of pregnancy, changes in the uterus are insignificant, and a doctor's examination to diagnose her condition is of no practical use. To diagnose pregnancy after a two-week delay in menstruation, it is recommended to do an ultrasound examination of the uterus. The doctor, using a transvaginal sensor, will be able to determine the level of development 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 with the help of palpation and make an assumption about the gestational age.

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 into the vagina of a pregnant woman, and with his left hand gently palpates the anterior 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 worth refraining from such manipulation in diagnosed isthmic-cervical insufficiency, which leads to a critically early opening of the cervix.

From the 4th month of pregnancy, the observing doctor beginsapply Leopold-Levitsky techniques: 4 ways 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 taken very carefully so as not to increase the tone of the uterus and the muscles of the abdominal wall.

The first step 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 palms on the highest point of the uterus and, gently pressing, evaluates its height and correspondence to the month of pregnancy. It is also determined whether the head or pelvic end is in the bottom with the child in the longitudinal position. The head has a dense and rounded shape, and the pelvic region is larger. It may move with the child's body.

The second obstetric appointment 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 middle of the pregnant woman's abdomen and gently, alternately, feels the area under the palms. If the baby is in a longitudinal position, then legs and arms are determined on one side, and the back is on the other.

Using the third technique, the gynecologist evaluates the area of the child's body that is in the small pelvis and will be the first to pass through the birth canal. Another doctor determines the degree of omission of the presenting part. For this, the area above the symphysis is palpated. At the same time, the head has clearer boundaries than the pelvic end in the longitudinal position of the child.

Fourth palpation of the uterusis carried out in order to clarify the position of the presenting part in relation to the entrance to the small pelvis. If a child's head is presented, then it can be lowered into the small pelvis, 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.

Fundal height

Measuring the fundal height (FH) is a routine procedure carried out by the obstetrician at every appointment. It is used starting from the 4th month of pregnancy in order to clarify the intensity of the growth of the uterus and establish its relationship 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 symphysis to the highest point of the fundus of the uterus with a measuring 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 value of the WMD in centimeters is approximately equal to the gestational age in weeks.

During pregnancy, the height of the uterus is determined by many factors: multiple pregnancy, the 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. Therefore, when calculating the gestational age, all significant factors are taken into account, such as the day of the last menstruation and the results of an ultrasound examination.

Uterine height during pregnancy: norms
Weekpregnancy	WDM (in cm)
16	6-7
20	12-13
24	20-24
28	24-28
32	28-30
36	32-34
40	28-32

The uterus is an extraordinary female organ that preserves and gives life to a new person. Changes in the uterus during pregnancy are surprising and make you wonder how rational and beautiful the human body is.