How does the length of the cervix change during pregnancy? Changes in cervical length during pregnancy

The cervical canal is essentially the lumen of the cervical cavity. This anatomical formation connects the vagina (external environment) and the uterine cavity (internal environment). During menstruation, blood from the uterine cavity comes out through this lumen. And through it, male reproductive cells enter the uterus to then connect with the egg. During labor, the baby passes through this narrow and small canal without much effort. Thus, this organ can be considered completely different from any other muscular organ.

Important! In the absence of menarche in girls, a thorough gynecological examination should be performed. Perhaps the reason for the absence of menstruation lies in aplasia of the cervical canal - when its lumen is closed and there is no communication between the uterine cavity and the external environment. In this case, menstrual blood can accumulate in the uterine cavity and cause pain, and then an inflammatory process.

Anatomy of the cervical canal

The lumen of the cervix can have a different shape and length in different women. On average, the length of the cervical canal in an adult nulliparous woman is 35–40 mm. The shape of the canal depends on race, the structure of the pelvis and genital organs.

Along its length, the cervix has two narrowings, called the internal (closer to the uterus) and external (closer to the vagina) pharynx. The internal os canal communicates with the uterine cavity, the external os with the vagina and the external environment. During each trimester, the obstetrician-gynecologist evaluates the size and lumen of the external pharynx and, based on these data, determines the duration of pregnancy and the presence of a threat of premature birth.

The inside walls of the cervical canal cavity are covered with a special columnar epithelium. The cells of this epithelium produce a mucous secretion, the quantity and quality of which depend on hormonal levels.

Hormone levels vary on different days of the menstrual cycle. Accordingly, the onset of ovulation and the phase of the menstrual cycle can be determined by the quality of mucus. Also, assessing the quality of mucus allows us to identify various pathologies of the menstrual cycle and changes in the hormonal levels of the female body.

Interesting! A symptom of mucus tension - the gynecologist uses it to determine the saturation of a woman’s body with estrogen. Between the legs of the forceps, the mucus obtained when taking a smear from the cervical canal is stretched - the longer the thread, the more estrogen in the body.

Cervical mucus has bactericidal properties, which helps maintain sterility inside the uterine cavity. Mucus fills the cervical canal throughout pregnancy. During this period it is thicker and denser. Forms a mucus plug that performs a protective function. The cork protects the fetus from infection. Just before birth, the mucus plug comes off.

The mucus reaction is different in different phases of the menstrual cycle. During ovulation, when conception is most likely, the mucus becomes alkaline. For sperm, the alkaline reaction of the environment is most favorable. In addition, under the influence of estrogen, the mucus thins, and sperm are able to move faster.

Before and after ovulation, the mucus in the lumen of the cervix is thicker, and its reaction is acidic. This helps slow down the movement of sperm.

Interesting! It is on this property of mucus that the action of hormonal contraceptives is based. Hormones change the state of cervical mucus, and it does not allow sperm to enter the uterine cavity.

What determines the length of the cervical canal

The length of the cervical canal changes in each period of a woman’s life. In an adult nulliparous woman, the length of the cervical lumen does not exceed 40 mm, its width on average is 8 mm.

During pregnancy, the cervical cavity decreases in size - both in length and width. This is necessary in order to form a compacted muscle barrier for the growing fetus. Under the influence of gravity, the fetus, increasing in size, tends downward, towards the exit from the uterine cavity. The thickened and decreased lumen of the cervix does not allow the fetus to leave the uterine cavity and keeps it there until the time of physiological labor.

At the same time, the walls of the canal are so extensible that it can allow the baby’s head to pass through during childbirth. The mucous membrane of the cervical cavity is much thicker than the mucous membrane of the uterine cavity. In addition, on the front and rear walls of the canal it is collected in numerous folds. This folding contributes to the expansion of the cervical canal during childbirth and the passage of the fetus through it.

The muscular layer of the cervix is also slightly different from the muscular layer of the uterus. It has an increased content of elastic fibers, which also contributes to the greater extensibility of the canal.

The length of the cervix depends on a variety of external and internal environmental conditions. It can change under various pathological and physiological conditions.

With congenital pathology of the development of the genitals, for example, atresia of the cervical canal. In this case, the lumen of the cervix is partially or completely closed, and its length may decrease.
Expansion of the cervical canal is observed during various inflammatory processes in it.
The length of the cervical lumen can be affected by such a pathological condition as its stenosis.
A polyp of the cervical canal in most cases leads to its expansion. The length of the channel, as a rule, does not change. The polyp can be located in any part of the cervical canal mucosa.
The length of the cervical canal often changes due to various injuries - childbirth with a large fetus, surgery, abortion.
During pregnancy, throughout its entire duration, the length of the cervical canal should not be less than 35 mm. A decrease in this length indicates the development of cervical incompetence -. This condition threatens premature birth.

If the length of the cervical canal during pregnancy decreases to 22 mm, this indicates a possible risk of premature birth. The length of the cervical canal is considered critical if it is less than 15 mm. This is an indication for suturing the uterine isthmus.

A pregnant woman is prescribed several ultrasound examinations throughout her pregnancy. This is done precisely in order to monitor the condition of the cervical canal and timely notice the developing signs of isthmic-cervical insufficiency. Ultrasound allows you to accurately determine the length of the isthmus.

Important! If signs of isthmic-cervical insufficiency appear, the woman is hospitalized in the hospital to maintain the pregnancy. If conservative treatment fails, several stitches are placed on the cervix. These sutures hold the opening external os in the desired position and prevent the development of premature birth. The sutures are removed at the time when physiological labor is possible.

In the first trimester of pregnancy, the physiological length of the cervical canal is 40 mm. In the second trimester, the canal is shortened to 35 mm. At 36 weeks of pregnancy, the length of the canal is 30 mm. In the last week before childbirth, the cervix ripens. The channel reaches a length of 10 mm. There is an expansion of the canal and opening of the uterine pharynx. In the first stage of labor, the cervix smoothes and the external and then internal os gradually open. At this time, every half hour the obstetrician assesses the condition of the cervix and the woman’s readiness for childbirth.

If labor is weak, prostaglandins can be injected into the cervical canal - substances that enhance the contractility of the uterus.

When giving birth to a large fetus or with a narrow pelvis, a rupture of both the perineum and the cervix may occur. In this case, the lumen of the cervical canal increases and bleeding develops. To restore the integrity of the cervix, the obstetrician-gynecologist applies stitches. Within a month after the rupture, sexual rest is prescribed for complete healing. But even under such conditions, the shape and length of the cervical canal may change.

WHO SAID THAT IT IS HARD TO CURE INFERTILITY?

Have you been wanting to conceive a child for a long time?
Many methods have been tried, but nothing helps...
Diagnosed with thin endometrium...
In addition, for some reason the recommended medications are not effective in your case...
And now you are ready to take advantage of any opportunity that will give you the long-awaited baby!

Cervicometry is an ultrasound examination that allows you to determine the condition of the pharynx (internal and external), cervical (cervical) canal and its length. During gestation, the muscles of the uterus hold the fetus in its cavity; if muscle tone weakens prematurely, this leads to shortening of the cervix and its opening.

The smaller the cervical size, the higher the risk of losing the child. Ultrasound of pregnant women allows gynecologists to promptly identify signs of a threat of failure and prevent it.

Diagnostic standards for cervicometry during pregnancy

The length of the cervical canal, together with the external and internal pharynx, is a variable value. Their sizes depend on the duration of pregnancy and the number of births (primipara or multiparous woman). The longer the gestation period, the correspondingly the size of the cervical canal should be smaller (the canal is shorter). If the pregnancy is normal and there is no threat of miscarriage:

at 20 weeks, the normal dimensions are within 40 mm;
at 34 weeks - within 34 mm.

If the length of the cervix is less than 25 mm, then it is assessed as short, and the question of the threat of failure arises. If its dimensions are less than 15 mm. at the end of the second trimester - this is an indicator of a high risk of miscarriage.

Preparing for the study

This type of ultrasound does not require special preparation, diet, use of any medications or discontinuation of prescribed medications. It is enough to follow the usual hygiene procedures and have a diaper with you (cover the couch), as well as a medical condom (put it on the vaginal sensor/transducer). Before the procedure, you must empty your bladder. Ultrasound is performed using an intracavitary transducer. Normally, the procedure is painless; if discomfort occurs, you should immediately inform the doctor performing the procedure.

Cervicometry is performed using a special intracavitary ultrasound sensor and does not require special training for the woman.

Cervicometry procedure

There are several ultrasound methods that allow you to determine the size of the cervical canal along with the external and internal os. These methods include:

transabdominal ultrasound (through the abdominal wall), during which the bladder must be full;
transvaginal ultrasound (the transducer is inserted directly into the vagina).

Despite the presence of two methods, international standards for cervicometry require that the dimensions of the area under study on ultrasound be determined correctly, as accurately as possible from the external to the internal pharynx. This can only be done through examination performed through the vagina. A mandatory condition for its implementation is an “empty” bladder, because. during transabdominal examination, the bladder may cover the internal os. During the cervicometry procedure, the size of the cervix is assessed first of all - its length, as the main indicator of normality and pathology. Next, they study the expansion of the internal os, the condition of the cervical canal, and establish the presence of prolapse (protrusion) of the membranes in them with the development of ICI (isthmic-cervical insufficiency). If there is a suture in the area of the cervical canal, its location is specified.

There were no cases of any complications occurring during the study, immediately after the procedure or in the distant future. Like any ultrasound examination, transvaginal ultrasound is the safest, non-traumatic, accurate and informative method for determining the norm and pathology of the organ being examined. The method is safe for both the mother and her baby.

Transvaginal ultrasound is the most informative at the beginning of pregnancy. At the same time, the method is completely safe for both the woman and the unborn baby.

Timing of cervicometry

A control (screening) study is prescribed to all pregnant women, regardless of the fertility of the pregnancy and its primacy. The timing of cervicometry coincides with a screening study of fetal anatomy. If a woman has had problems with pregnancy in the past (late self-abortion, premature delivery), or with an established multiple pregnancy, this examination should be carried out at an earlier date. Between weeks 11 and 14, during the first screening test for genetic developmental abnormalities. If there is a threat of premature termination of pregnancy, ultrasound monitoring diagnostics may be prescribed at intervals of 14 days, and in some cases even 7 days.

Indications for cervicometry. Risk group

If you have had a history of self-abortion or early miscarriage, the risk of fetal loss during the current pregnancy increases (with one case of miscarriage, this risk is increased by 5-10%; if there have been several cases of self-abortion, the risk increases to 20%). With multiple births, the risk of miscarriage in the third trimester increases significantly. When carrying one fetus, the risk of miscarriage is up to 1%; when carrying dichorionic twins, the risk is already about 5%; when carrying monochorionic twins, the risk increases by an order of magnitude and is 10%.

For the same reason, when undergoing an ultrasound scan of the fetus at any stage of gestation, a woman should inform the doctor about a history of premature birth/self-abortion, surgical interventions on the cervical canal, i.e. that she is at risk.

Risk group that requires close monitoring of the gestation process:

the presence of self-abortion in the later stages or premature delivery of previous pregnancies;
suspicion of ICN;
multiple births;
surgical interventions and sutures on the cervical canal.

Shortening of the cervix (SCI)

One of the most common pathologies is isthmic-cervical insufficiency (ICI), shortening of the isthmus and cervix. The condition of ICI is diagnosed when the size of the organ does not exceed 25 mm. Reasons causing shortening of the cervix:

Large or multiple pregnancies, as well as polyhydramnios in women who have suffered traumatic exposure to the cervical canal.
Hereditary abnormalities of the structure of the uterus. This pathology is very rare.
Violation of hormonal status during pregnancy. This is due to the activation of the fetal adrenal glands (in the third month of gestation). If a woman’s blood level of androgens is normal, this is not critical, but if it is elevated, then the additional amount of these hormones secreted by the fetal adrenal glands leads to a decrease in the size of the cervical canal. This happens asymptomatically, because is not accompanied by an increase in muscle tone of the entire organ.
Mechanical injuries to the cervix with subsequent deformation (for example, when applying medical forceps) due to abortions, diagnostic curettages, etc.

Multiple pregnancies and large fetal weight directly lead to shortening of the cervix

The development of ICI can be indicated by the opening of the internal pharynx in the form of a funnel, revealed by ultrasound examination. In the normal state it is closed. Additional reasons for ICI may be:

excision of the cervical canal during the treatment of certain types of pathologies;
trauma to the cervical canal during previous births;
his injuries as a result of self- or medical abortions.

Such a pathology requires hospitalization and, in the future, if the condition does not return to normal, possible intervention. For this purpose, bed rest is recommended, or a suture is placed (cervical cerclage) on the neck, or special mechanical devices are installed. These devices are used to support the uterus and are called an obstetric pessary.

Shortening the cervical canal is not a death sentence. This is only a signal that the risk of miscarriage has increased and it is necessary to reduce the intensity of physical activity, and, if necessary, carry out preventive measures in a timely manner.

Immaturity of the cervix during ultrasound examination

There is also the opposite problem - the cervix is not ready for the process of delivery (immaturity), despite the pregnancy being full-term. The reason for this may be psychological problems (fear of the process of childbirth), anatomical anomalies in the development of the organ, or operations, as a result of which the walls of the cervical canal lose their elasticity. Readiness is assessed on a 3 or 4 level scale. 3-level scales are more often used. The main signs of the uterus being ready for delivery (maturity) are:

its structure, which is usually described as consistency;
patency of the cervical canal;
length of the vaginal part;
deviation from the wire pelvic axis.

The degree of maturity of the cervix is assessed in points:

Characteristic value	Degree of maturity, score
	0	1	2
consistency	dense	softened, except for the area of the internal pharynx	soft
length, cm/smoothness	more than 2 cm	1-2 cm	less than 1 cm/smoothed
patency of the cervical canal	the external pharynx is closed, allowing the first phalanx of the finger to pass through	the cervical canal is passable for 1 finger, there is a seal of the internal pharynx	more than 1 finger, with a smoothed neck more than 2 fingers
position	posteriorly	anteriorly	median

The degree of its maturity according to a 3-level system is assessed in points from 0 to 10. From 0 to 3 points - immature, from 4 to 6 - maturing and from 7 to 10 - mature. Normally, after 37 weeks, the transition from an immature to a mature state occurs. If the uterus is immature or poorly mature, problems arise during delivery. An operation - caesarean section - may be indicated.

Methods for preventing premature pregnancy

In modern obstetric practice, the most effective methods are considered to be drug prevention and surgical intervention (suturing the cervix). Suturing (cervical cerclage) is considered an effective way to prevent premature birth. There are two options for this intervention. In the first case, sutures are placed at the end of the first trimester. In the second case, monitoring ultrasound diagnostics is performed. Its duration is from 14 to 24 weeks with an interval of 14 days. Surgical intervention in this case is considered justified if the length of the neck is reduced to 25 mm or less. The second approach reduces the need for surgery by up to 50%. However, this operation is risky for multiple pregnancies and may increase the risk of premature delivery.

Progesterone preparations are used as medications to prevent early delivery. Also, placement of a vaginal pessary is used as an experimental technique. After using mechanical or surgical means to prevent early delivery, transvaginal ultrasound is not performed.

The length of the cervix during pregnancy, depending on the period, changes in one direction or another. What is considered the norm and what is a deviation?

Anatomical description

The cervix is made up of muscle tissue and serves to connect the uterus and vagina. Inside it is the cervical canal, with the help of which the uterus is able to cleanse itself of the rejected endometrial layer during menstruation. The connection of the uterus with the cervical canal is called the internal os, and the opening connecting the vagina and the cervical canal is called the external os. If there is no pathology during pregnancy, the cervical canal is in a closed position and is blocked by a plug of mucus, which eliminates the possibility of infection of the fetus.

This mode of existence continues until 37 weeks, after which the cervix prepares for the upcoming birth. From this moment, the pregnancy is considered full-term, and important changes begin in the structure of the cervix, it softens, opens slightly and tries to take a central position. These changes make it possible to create a straight canal with the uterine cavity, which expands by more than 10 centimeters during childbirth, and after the end of labor returns to its previous size. The external external os of the cervical canal becomes slit-like, in contrast to nulliparous patients, whose external external os looks like a point.

To protect against the penetration of infection into the genital organs, a mucous plug is designed to close the entrance to the external birth canal. Before giving birth, she leaves her place entirely or comes out in parts. This process allows us to consider the moment of the beginning of labor.

The role assigned to the cervix in a woman’s body cannot be overestimated. This organ takes an important part in pregnancy and the birth process. During different periods of pregnancy, its length changes depending on the period and these changes must comply with certain standards. Cases of length deviation in one direction or another can lead to fetal death, termination of pregnancy and miscarriage. The retention of the fetus in the uterus during pregnancy depends on the length of the cervix; if a pathology occurs in the structure, there may be a threat to further pregnancy.

Changes occurring in the cervical canal of the uterus occur in accordance with hormonal changes in the body of a pregnant woman. Due to increased blood circulation in the muscles of the outer walls of the uterus, a bluish tint appears, noted during a gynecological examination. At the same time, a conclusion is made about the correspondence of the length of the cervix to the week of pregnancy and the amount of cervical mucus in the vagina of a pregnant woman according to generally accepted norms for this period. The layer of internal epithelium, under the influence of an increase in estrogen in the body of a pregnant woman, also thickens, which leads to a significant increase in the volume of the main reproductive organ of a woman - the uterus.

Constant medical supervision during pregnancy allows you to monitor the process of bearing a child and the condition of the body as a whole. Tracking the length of the cervix week by week helps prevent the occurrence of pathologies in the female reproductive organs and in the cervical canal. The specialist is constantly paying attention to several indicators on which successful pregnancy and successful delivery depend. This is especially true for patients who have been diagnosed with threatened miscarriage:

the content of cervical mucus located in the cervical canal;
the length of the cervical canal and the elasticity of its walls.

Based on indicators that correspond to the norm, a conclusion can be made about the correct development of the fetus and the absence of pathology that could negatively affect the child.

Measurement methods

Two methods are used to examine the cervix:

A vaginal examination by a gynecologist determines the length, relationship to the pelvic axis, and size of the cervical canal. A similar examination is carried out at all visits to monitor changes occurring during fetal development.
Ultrasound examination, which allows you to evaluate the external and internal pharynx of the cervix, with determination of the length of the cervical canal itself.

Control measurements of the cervix are carried out from the twentieth week of pregnancy, due to the fact that before this period its size depends on the individual characteristics of the physical structure. After overcoming this threshold, close monitoring of all changes occurring in the cervix begins, in order to prevent cases of pathology developing in it and deviations from the norm in accordance with a certain period of pregnancy.

To do this, the gynecologist performs a repeat screening ultrasound to determine the condition of the organs. In the case of determining shortened sizes, there is a need for an additional transvaginal examination of the woman with the insertion of a sensor into the vaginal cavity, which allows a more accurate determination of the length of the cervical canal.
Ultrasound examination allows us to determine the presence of pathologies in the condition of the neck with a length of less than 25 millimeters and the funnel-shaped expanded state of the internal pharynx, which should be in a closed state.

A pathological change can occur for many reasons, in the case of traumatic surgical interventions as a result of abortions or previous births, previous diseases and the anatomical characteristics of the woman. There are also cases of cervical immaturity, which occurs due to a psychological state due to fear of the upcoming birth, as well as due to congenital developmental defects. In these cases, the cervix becomes inelastic and poorly extensible, which can cause injury during the movement of the child through the cervical canal during childbirth or during a cesarean section.

Changes by week

The length of the cervix by week during pregnancy is measured in millimeters. During these periods, sizes may vary:

cervical length up to 12 weeks - up to 36 mm;
cervical length from 12 weeks - up to 39 mm;
cervical length in the third trimester - up to 41 mm;
The length of the cervix after 29 weeks is reduced to 37 mm.

During this period, the body begins to prepare for the upcoming labor.

Important! The control group includes patients with pathological abnormalities during pregnancy, as well as those who have injuries to the cervix or premature shortening of the cervix in a previous pregnancy. They require close monitoring of their condition starting from the 16th week.

Interesting video:

Short cervix

A short cervix is a dangerous pathology that threatens normal gestation and the risk of possible miscarriage at all stages of pregnancy. This developmental deviation is possible for several reasons:

as a result of hormonal imbalances;
presence of scars;
complications from previous infections;
the presence of inflammation in the pelvic area.

Premature shortening can lead to an inability to retain the fetus in the uterine body. Unable to bear the weight, the cervix threatens to dilate, which will lead to premature labor and the birth of a non-viable fetus. A woman is at risk of miscarriage when the cervical length is 25 millimeters or less when the internal os opens.

If there is a threat of miscarriage due to this pathology, hormonal treatment, installation of a pessary or sutures placed on the cervix are prescribed. This will prevent premature dilatation and preserve the pregnancy until a certain period. The sutures are removed at 38 weeks, when the fetus reaches a certain size and is considered full-term. From this moment the reproductive function begins and the birth begins.

Long cervix

Often, when examined by a gynecologist, a long cervix is determined. This deviation does not entail consequences for the pregnant woman and does not pose a threat of miscarriage or possible miscarriage. The length of the cervix and cervical canal above normal can cause complications during the birth itself if it is not subject to changes. A long, tight cervix will not be able to fully open as the baby moves through the cervical canal. This deviation can lead to the inability to deliver naturally and to remove the baby by caesarean section. To avoid this situation, when this deviation is detected in the structure of an important organ - the cervix, measures are taken to soften and smooth it to make it more elastic.

Cervical length before birth

Changes occurring in the cervix and cervical canal are necessary for the preparation and further opening of the birth canal. After the 37th week, the cervix prepares for labor; it shortens and softens. Changes also occur in the external pharynx; upon examination by a gynecologist, its opening is found to be the size of a fingertip. The duration of the changes in time is different for all patients; some women go through this period three to five hours before the onset of contractions, for others this moment can last up to several days or weeks.

The onset of labor occurs with the occurrence of cramping attacks, repeated at certain intervals and when the external pharynx opens more than 10 cm. After the birth of the child, the cervix returns to its normal state, characteristic before childbirth.

Important! The length of the cervix by week is one of the important constantly changing indicators of the ongoing pregnancy. Shortening and softening it in the early stages indicates a possible threat to the successful course of pregnancy and the possibilities of preventing it. The absence of such symptoms in the later stages also signals that the woman’s body is unprepared for the birth process and also requires timely medical assistance.

Cervix and infertility

Recently, there has been an unpleasant trend that continues to increase over time. Low birth rate is one of the most important problems in the development of the demographic situation of our country, affecting the processes occurring in the economy. If in the last century the main reason for this was called socio-economic, then at present the reason for low fertility is the spread of various pathologies in women's health and, as a consequence, frequent infertility and the impossibility of procreation. A major role in this issue is played by deviations in the development of the reproductive system and in pathological changes in the cervix and its cervical canal. Modern medicine takes this area very seriously and has achieved significant success in it. If desired, almost any couple with the help of modern diagnostic methods can achieve and maintain pregnancy until the birth of full-fledged offspring.

As it turns out, the question of cervical dilatation, the timing and size of the opening in centimeters or transverse fingers and how to interpret this worries all pregnant women. However, many do not know a clear answer. We will try to cover this topic as much as possible and start with the anatomical features.

The uterus is an important organ of a woman's reproductive system and consists of the body of the uterus and the cervix. The cervix is a muscular tubular formation that starts from the body of the uterus and opens into the vagina. The part of the cervix that is visible when examined in speculums is called the vaginal part. The internal os is the transition of the cervix into the uterine cavity, and the external os is the border between the cervix and the vagina. In these places the muscle part is more pronounced.

During pregnancy, some of the muscle fibers in the cervix are replaced by connective tissue. Newly formed “young” collagen fibers are stretchable and elastic; when they are formed excessively, the cervix shortens and the internal os begins to expand.

Normally, throughout pregnancy, the cervix is long (about 35 - 45 mm), and the internal os is closed. This position helps prevent spontaneous miscarriage and also protects against infection entering the uterine cavity.

Only a few weeks before the expected date of birth (EDD), the cervix changes its structure, gradually becoming softer and shorter. If shortening, softening of the cervix and expansion of the internal os occurs during pregnancy, then this condition threatens termination of pregnancy or premature birth.

Causes of premature shortening of the cervix:

Aggravated obstetric history (abortions, miscarriages at different stages, history of premature birth, especially very early premature birth before 28 weeks)

Aggravated gynecological history (infertility, polycystic ovary syndrome and other gynecological diseases)

Cervical injuries (surgeries, ruptures in previous births, large fetus births)

Norms for the cervix by timing

Up to 32 weeks: the cervix is preserved (length 40 mm or more), dense, the internal os is closed (according to ultrasound results). On vaginal examination, the cervix is firm, deviated posteriorly from the pelvic axis, and the external os is closed.

The wire axis of the pelvis is a line connecting the midpoints of all direct dimensions of the pelvis. Since the sacrum has a bend, and then the birth canal is represented by the muscular-fascial part, the wire axis of the pelvis is represented by a curved line, reminiscent of a fishhook in shape.

32–36 weeks: the cervix begins to soften in the peripheral parts, but the area of the internal os is dense. The length of the cervix is approximately 30 mm or more, the internal os is closed (according to ultrasound). On vaginal examination, the cervix is described as “tight” or “unevenly softened” (closer to 36 weeks), deviated posteriorly or located along the wire axis of the pelvis, the external pharynx in primiparous women may allow the tip of a finger to pass through, in multiparous women it allows 1 finger into the cervical canal.

From 37 weeks: the cervix is “mature” or “ripening”, that is, soft, shortened to 25 mm or less, the pharynx begins to expand (the length of the cervix, the funnel-shaped expansion of the uterine pharynx, is described by ultrasound). On vaginal examination, the external os may allow 1 or 2 fingers to pass through, the cervix is described as “softened” or “unevenly softened”, located along the wire axis of the pelvis. At this time, the fetus begins to lower its head into the pelvis and puts more pressure on the neck, which contributes to its ripening.

To assess the cervix as “mature” or “immature”, a special table (Bishop scale) is used, where the parameters of the cervix are assessed in points. Nowadays, the modified Bishop scale (simplified) is most often used.

Interpretation:

0 – 2 points - the cervix is “immature”;
3 – 4 points - the cervix is “not mature enough”
5 – 8 points - the cervix is “mature”

The ripening of the cervix begins in the area of the internal os. For primiparous and multiparous women, the process occurs slightly differently.

In primigravidas (A), the cervical canal becomes like a truncated cone, with its wide part facing upward. The fetal head, falling down and moving forward, gradually stretches the external pharynx.

In multiparous women (B), the expansion of the external and internal os occurs simultaneously, so repeated births, as a rule, proceed faster.

1 – internal pharynx
2 – external pharynx

Cervix during labor

Everything we described above applies to the condition of the cervix during pregnancy. During pregnancy, the terms “shortening of the cervix”, “dilation of the internal os”, “cervical maturity” are used. The term “dilation” or “opening” (they mean the same thing) begins to be used only with the onset of labor.

By the time of birth, the cervix, gradually shortening, is completely smoothed out. That is, it ceases to exist as an anatomical structure. The long tubular structure is completely smoothed out and only the concept of the “internal os of the cervix” remains. Its opening is calculated in centimeters. As labor progresses, the edges of the internal os become thinner, softer, and more pliable, which makes it easier for the fetal head to stretch them.

Depending on the degree of opening of the internal pharynx, labor is divided into periods I and II:

I stage of labor This is what is called “the period of dilatation of the internal os of the cervix.” The first period is divided into phases.

During the latent (hidden) phase, the internal os gradually opens up to 3–4 cm. Contractions during this period are moderately painful or painless, short, occurring in 6–10 minutes.

Then the active phase of the first stage of labor begins - the rate of opening of the uterine pharynx should be at least 1 cm per hour in primiparous women and at least 2 cm per hour in multiparous women, contractions in this period become more frequent and occur once every 2 to 5 minutes, becoming longer ( 25 – 45 seconds), strong and painful.

The internal os should open to 10 - 12 cm, then this is called “full opening/dilatation” and the second stage of labor begins.

II stage of labor called the period of “expulsion of the fetus.”

At this stage, the uterine os is fully opened, and the fetal head begins to move along the birth canal towards the exit.

The dynamics of the opening of the uterine pharynx is reflected in the partogram, which is maintained from the beginning of the latent phase and is filled out after each obstetric examination.

A partogram is a method of graphically describing childbirth, which reflects in the form of a graph the dilatation of the cervix in centimeters, time in hours, the advancement of the fetus along the pelvic planes, the quality of contractions, the color of the amniotic fluid and the fetal heartbeat. Below is a simplified version of the partogram, which reflects only the parameters that interest us in this topic, that is, the opening of the uterine pharynx over time.

In order to clarify the obstetric situation, the doctor conducts an internal obstetric examination, the frequency of which depends on the period and phase of labor. In the latent phase of the first period, the examination is carried out once every 6 hours, in the active phase of the first period, once every 2-4 hours, in the second period, once per hour. If any deviation from the physiological course of labor develops, the examination is carried out according to indications over time (the frequency of examinations is determined by the doctor leading the birth, examination by a council of doctors is possible).

Pathologies associated with the process of cervical dilatation:

1) Pathological condition associated with shortening of the cervix and/or expansion of the internal os during pregnancy:

2) Pathology of cervical dilatation in the preliminary period.

The preliminary period is a condition with rare, weak cramping pain in the lower abdomen and lower back, develops with full-term pregnancy and a mature cervix, lasts about 6 - 8 hours and gradually progresses into the first stage of labor. The preliminary period is not observed in all women.

The pathological preliminary period is irregular short painful contractions with a mature cervix, which last more than 8 hours and do not lead to cervical effacement.

3) Pathologies of cervical dilatation during childbirth.

-weakness of the ancestral forces. Weakness of labor forces is the contractile activity of the uterus that is insufficient in strength, duration and regularity. Weakness of labor is manifested by a slow rate of dilatation of the cervix, rare, short, insufficient contractions that do not lead to the advancement of the fetus. This diagnosis is made based on observation of the pregnant woman, the results of carditocography (CTG) and vaginal examination data. The above figure shows the result of CTG with weak labor forces, as we see contractions here of weak strength and short duration. For comparison with the norm, we provide the figure below.

Primary weakness of labor forces is a condition when contractions initially did not become sufficiently effective.

Secondary weakness of labor forces is a condition in which the developed regular and effective labor activity fades away and becomes ineffective.

- discoordination of labor. Discoordination of labor is a pathological condition in which there is no coordination between contractions of different parts of the uterus, contractions are uncoordinated and can be very painful if they are unproductive (the fetal head does not move along the birth canal). For example, the fundus of the uterus is actively contracting, but the cervix (uterine pharynx) is not opening sufficiently, or the cervix is opening, but the fundus of the uterus is not contracting effectively enough. The figure below shows the result of CTG during discoordinated labor, contractions have different strengths and frequency.

A form of incoordination of labor, in which the body of the uterus actively contracts, and the cervix does not have sufficient dilatation due to scar changes (consequences of abortion, old ruptures, cauterization of erosion) or an undiagnosed condition (there is no indication of pathology or trauma to the cervix in the history) is called dystocia cervix. This form of pathology is characterized by painful nonproductive contractions and pain in the sacral area. During an internal obstetric examination, the doctor sees a spasm of the uterine pharynx during contractions and rigidity of the edges of the internal pharynx of the cervix (tightness, inflexibility).

- rapid and rapid birth. Normally, the duration of the labor process is 9–12 hours; for multiparous women it may be less, approximately 7–10 hours.

For first-time mothers, a rapid birth is considered to be a birth of less than 6 hours, and a rapid birth is considered to be less than 4 hours.

In multiparous women, rapid labor is considered to be labor of less than 4 hours, and rapid labor is considered to be less than 2 hours.

Fast and rapid labor is characterized by an accelerated rate of opening of the cervix and expulsion of the fetus. In some cases, this is a blessing, since delay can lead to complications (pathologies of the umbilical cord, placenta, and others). But often, due to the rapid pace of labor, the child does not have time to correctly go through all the stages of the biomechanism of childbirth (adaptation of the soft bones of the child’s skull to all the bends of the mother’s pelvic bones, timely turns of the body and head, flexion and extension of the head), and the risk of birth trauma is increased (as in mother and newborn).

Treatment for premature cervical dilatation:

1) Isthmic - cervical insufficiency treated by placing circular sutures on the cervix (from 20 weeks) or installing an obstetric pessary (from approximately 15-18 weeks).

2) Pathological preliminary period. After the observation period has expired (8 hours) and there is no dynamics during a repeated vaginal examination, an amniotomy is performed (opening the amniotic sac). If the cervix remains shortened, but does not smooth out, then oxytocin may be administered to stimulate labor. If the cervix has smoothed out, but there is no regular labor, then they talk about the transition of the pathological preliminary period into primary weakness of labor.

3) Weakness of generic forces. Amniotomy is performed as the first treatment measure for weak labor. After amniotomy, dynamic monitoring of the woman in labor, counting of contractions, CTG monitoring of the fetal condition and obstetric examination after 2 hours are indicated. If there is no effect, drug treatment is indicated.

With primary weakness, labor is induced, with secondary weakness, labor is intensified. In both cases, the drug oxytocin is used, the difference is in the initial dose and the rate of delivery of the drug through the infusion pump (drip dosage administration). If there is no effect of treatment, delivery by cesarean section is indicated.

4) Discoordination of labor (cervical dystocia). When discoordinated labor develops, the woman in labor must undergo labor anesthesia using narcotic analgesics (promedol intravenously in an individual dose under CTG control) or therapeutic epidural anesthesia (single injection of anesthetic or prolonged anesthesia with periodic administration of the drug). The type of anesthesia is selected individually after a joint examination by an obstetrician-gynecologist and an anesthesiologist-resuscitator. If there is no effect of treatment, delivery by cesarean section is indicated.

5) Rapid and rapid birth. In this case, the most important thing is to end up in a maternity facility. It is impossible to stop labor, but it is necessary to monitor the condition of the mother and fetus as carefully as possible. Cardiotocography is performed (the main thing is to clarify the condition of the fetus, whether there is hypoxia), and, if necessary, ultrasound examination (suspecting placental abruption). In the case of a rapid birth, there must be a neonatologist (micropediatrician) in the delivery room and there must be conditions for providing resuscitation care to the newborn. Caesarean section is indicated in the event of an emergency clinical situation (placental abruption, acute hypoxia or incipient fetal asphyxia)

After reading the article, you realized what an important and unique formation the cervix is. Pathologies of the cervix and in particular pathologies of cervical dilatation, unfortunately, do and will continue to occur, but any deviations from the norm can be treated the more successfully the sooner you see a doctor. And then the chances of maintaining your health and the timely birth of a healthy baby increase significantly. Take care of yourself and be healthy!

Obstetrician-gynecologist Petrova A.V.

The cervix is the organ directly responsible for maintaining pregnancy.

Not only the nature of the pregnancy, but also the development of the birth process depends on its condition.

One of the indicators characterizing the condition of the neck is its length. At different periods of gestation, the length of the cervix must correspond to certain standards, otherwise the likelihood of various pathologies increases.

The cervix is a muscular organ in the form of a tube through which the uterus and vagina are connected. Inside the cervix is the cervical canal, through which menstrual fluid is discharged.

The opening connecting the uterine cavity with the cervical canal is called the internal os, the cervical canal and vagina are called the external os.

Normally, the cervical canal during pregnancy should be closed and sealed with a mucus plug, protecting the fetus from infectious attacks.

The primary task of the cervix during the period of bearing a child is to keep it in the uterine cavity. If for some reason the cervix is unable to do this, there is a real threat of miscarriage.

The condition of the cervix can be determined by measuring its length, therefore, from a certain stage of pregnancy, this indicator should be monitored by the attending physician.

Methods for measuring cervical length

The cervix is examined in two ways:

During a gynecological examination on a chair. The doctor evaluates the density of the cervix, its length and location relative to the pelvic axis, and the condition of the external pharynx.
Using ultrasound. During the study, the length of the neck, the condition of the external and internal pharynx are determined.

Until the middle of the second trimester, the length of the cervix is very variable, so its control begins from the 20th week.

The “equator of pregnancy” is characterized by rapid growth of the fetus, so the load on the cervix increases.

From this point on, periodic monitoring of the condition of the cervix is necessary, which will allow timely detection of pathological changes.

Just at this time, the woman undergoes a test, during which the condition of the cervix is further assessed. Typically, at this stage, an ultrasound is performed transabdominally (the doctor moves the sensor across the abdomen).

But if a shortening of the cervix is suspected, an additional transvaginal examination is prescribed (a sensor is inserted into the vagina).

This method of examination allows you to more accurately measure the length of the cervix.

Change in length by week: table of norms during pregnancy

Normally, the cervix should be tight throughout most of pregnancy, and the internal and external pharynx should be closed. Depending on the stage of pregnancy, the length of the cervix must meet certain standards.

Table: Cervical length by week of pregnancy

From 16 weeks, regular monitoring of the condition of the cervix is indicated for pregnant women with a complicating medical history.

The risk group includes women with cervical damage as a result of surgical interventions, as well as those who were diagnosed with premature shortening of the cervix in a previous pregnancy.

Short cervix

Causes of premature shortening of the cervix:

hormonal disorders;
scars from abortion, surgery, or rupture of the cervix during a previous birth;
inflammatory diseases of the pelvic organs;
infections suffered by the expectant mother during pregnancy;
anatomical features of the structure of the internal genital organs.

A short cervix is a dangerous pathology that threatens the normal course of pregnancy.

Smoothing of the cervix can provoke (ICN). With this pathology, the cervix is not able to hold the fetus in the uterus. Under its weight, the cervix opens and a miscarriage occurs.

The threat of premature birth is identified when the length of the cervix is less than 25 mm and the opening of the internal pharynx.

Infants born as a result of ICI are extremely preterm and often die during childbirth.

To avoid such an ending, patients diagnosed with ICI are under close medical supervision. They are prescribed bed rest and most often admitted to a hospital.

Sometimes ICI can be suspected by bursting pain in the vagina, which radiates to the lower back and groin. But in some cases, the pathological process is asymptomatic, and nothing bothers the woman. This is what determines the need to control changes in neck length.

These measures help prevent premature dilatation of the cervix. The pessary and sutures are usually removed at 38 weeks of pregnancy, when the fetus is considered full-term. Often after this, women will soon begin labor.

Long cervix

Exceeding the established standards is possible in the following cases:

anatomical features of the cervical structure;
surgical interventions;
violation of the formation of a generic dominant - a depressed psychological state, fear of childbirth.

A long cervix does not affect the course of pregnancy in any way. If, as the date of birth of the child approaches, its length does not change, this condition can complicate the course of the birth process.

A long, dense neck (obstetricians call it “oak”) will dilate poorly during contractions, and may not dilate at all. In this case, the woman in labor will undergo an emergency caesarean section. To avoid this, during the period of preparation of a woman for childbirth, special treatment is prescribed to help smooth and soften the cervix.

Changes in the cervix before childbirth

After 37 weeks, the cervix begins to prepare for childbirth. It shortens, softens and centers itself relative to the pelvis.

The external os begins to miss the tip of the finger during a gynecological examination. The length of the neck during this period is reduced to 10-15 mm.

The duration of these changes varies from person to person. For some women, this process takes from several days to several weeks, for others, the cervix smoothes out several hours or a day before the onset of contractions.

Measuring and assessing the dynamics of cervical length is an important component in the prevention of miscarriage and premature birth. If a pathological decrease in the length of the cervix was detected in a timely manner, the chances of maintaining the pregnancy are high.

With the help of certain medications, a pessary and surgical procedures, shortening can be stopped. Assessment of cervical dynamics is also important during full-term pregnancy. By measuring the length of the cervix, you can determine how the body is preparing for childbirth and, if necessary, speed it up.