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Starting from the 38th week of pregnancy, the fetus in the womb fully matures, all its organs and systems are ready for independent work. That is why the period from 38 to 42 weeks is the ideal time for the birth of a child. However, in some cases, birth occurs earlier than expected. What are the dangers of premature birth, how does it begin and what measures need to be taken to maintain the health of the baby and mother?
What births are considered premature?
Preterm birth is birth that occurs before 22 to 37 weeks of pregnancy. The number of such births worldwide is about 6-9%. At the same time, premature birth is usually divided according to the stage of pregnancy, since there is a huge difference between a child born at 29 weeks and one born at 34 weeks of pregnancy. Meanwhile, in both of these cases the birth will be considered premature.
- premature birth at 22 - 28 weeks is classified as very early, since the weight of the child during this period ranges from 500 g to 1 kg;
- early premature birth occurs between 29 and 33 weeks. The weight of a newborn is about 2000 g;
- premature birth between 34 and 37 weeks. As a rule, during this period of time a child is born with a body weight of about 2500 g.
According to statistics, the majority of premature births (up to 60%) occur between 34 and 37 weeks of pregnancy; at up to 30 weeks this happens much less frequently. Until 1993, in our country, births that began no earlier than the 29th week of pregnancy were considered premature, and resuscitation measures were taken only for those newborns whose weight reached 1000 g. However, later in the Russian Federation new criteria recommended by WHO were introduced. Now intense medical care are required to provide care to all infants born at 22 weeks and weighing at least 500 g. It is worth noting that newborns with very low weight (up to 1000 g) must be registered with the registry office only if they have lived for more than 7 days ( 168 hours). If the fetus died during this time, then they speak of spontaneous termination of pregnancy (late miscarriage).
Causes of premature birth
There are a number of factors that cause premature birth. The reasons leading to miscarriage are divided into two groups.
1.Health of the expectant mother
These include endocrine diseases leading to dysfunction of the ovaries, thyroid gland, adrenal glands, pituitary gland, and pancreas. These diseases can cause a decrease in hormones responsible for pregnancy. Also, the general physical health of the expectant mother is very important for the normal course of pregnancy. If a woman suffers from heart disease, there are problems with the liver or kidneys, then the body begins to perceive pregnancy as a risk to life. And as a result, there is a threat of premature birth.
Another reason for miscarriage is anatomical changes in the reproductive organs. Underdevelopment of the uterus (infantilism), abnormal development of the uterus (one-horned, with a septum, two-horned), as well as various tumor processes, scars after caesarean section, injuries during induced abortions- all this can provoke premature birth. Special meaning has isthmic-cervical insufficiency (ICI) - pathological change cervix, in which, as pregnancy progresses, it loses the ability to hold the fetus in the uterine cavity. ICI is rarely congenital; most often it develops as a result of ruptures and injuries of the cervix during induced abortion or complicated childbirth. In some cases, ICN is formed when hormonal disorders in a woman’s body, for example, with an increase in male sex hormones in the blood.
The presence of infections in a woman’s body also plays an important role. First of all, this applies to diseases of the genitourinary system: inflammation of the uterus, appendages, ovaries, bacterial vaginitis. Hidden infections that did not manifest themselves before pregnancy pose a great threat: mycoplasmosis, chlamydia, urethroplasmosis, trichomoniasis, herpes, staphylococcal, streptococcal and cytomegalovirus infections. In addition, the presence of other acute or chronic diseases, such as viral hepatitis, tonsillitis, caries, often leads to serious complications. The main danger is that the infection can penetrate the amniotic membranes, thereby causing intrauterine infection of the fetus.
2. Course of pregnancy
Some pregnancy complications can trigger premature birth:
- severe gestosis, threatening the life of mother and child;
- placental insufficiency, characterized by impaired delivery of nutrients and oxygen to the fetus;
- detachment or premature aging placenta;
- incorrect position of the fetus (pelvic, transverse, oblique);
- overstretching of the uterine walls during multiple pregnancy or polyhydramnios;
- placenta previa;
- Rhesus conflict;
- woman's age.
Often the cause of termination of pregnancy is abnormal development of the fetus (mutations, genetic diseases, vices). Also a provoking factor is poor nutrition, hard physical labor, stress, bad habits(alcoholism, drug addiction, smoking).
Features of premature birth at different stages of pregnancy
Premature birth is very early stages(22 - 29 weeks) are often caused by isthmic-cervical insufficiency, infection in the membranes and premature rupture amniotic fluid. Childbirth before 30 weeks is the most dangerous and has the most severe consequences for the child. Such children are born with a critically low weight (less than 1000 g) and are often not viable. They cannot breathe on their own because the lungs do not have time to fully develop at this stage. Unfortunately, many babies subsequently have serious health problems (cerebral palsy, deafness, blindness).
To date, there is information about babies born in the early stages (22-23 weeks) who survived after resuscitation measures. However, the further prognosis for such children is extremely unfavorable. As a rule, they are all profoundly disabled with severe damage to the central nervous system.
Early labor at around 30 weeks can cause various factors: incompatibility of the fetus and mother by Rh factor or blood group, as well as other pathologies of pregnancy. The weight of such newborns ranges from 1000 to 2000. Despite the fact that their organs are not fully mature and work extremely unstable, with the help of modern drug treatment doctors manage to achieve excellent results. Most babies born at 28-34 weeks go on to lead full lives.
Childbirth at 34-37 weeks can be caused by hormonal imbalance, placental insufficiency, stress, injury or chronic diseases heart, kidneys, lungs. For children born at this stage, the prognosis is the most favorable. Their weight is approximately 1800-2500 g, and such babies are already quite ready for life outside the womb, but subject to special care.
Stages of premature birth
There are several stages of labor: threatening, beginning and active labor. This separation helps determine whether it is possible to wait longer and thereby prevent early appearance baby into the world. Therefore, the first signs of premature birth should not be ignored by specialists.
With threatening premature birth, aching, nagging pain in the abdomen or lower back, accompanied by tension of the uterus, is observed. The woman herself can feel slight contractions of the uterus, while the fetus begins to actively move. In addition, slight bleeding from the birth canal may appear. Having discovered the first signs of premature birth, the expectant mother should urgently consult a doctor!
The onset of labor is characterized by severe, cramping pain in the abdomen, the passage of a mucus plug or the presence of sanguineous discharge. Amniotic fluid may also leak or leak. During the examination, the doctor discovers that the cervix is dilated by 1-2 cm, while it shortens. Thus, all the signs characteristic of the onset of natural labor appear.
When labor begins, the symptoms are more pronounced: contractions become regular and strong, the uterine os opens by 2-4 cm or more. The membranes rupture, after which the presenting part of the fetus moves into the pelvis.
Common Complications
Spontaneous termination of pregnancy is often accompanied by various complications. This may be abnormal labor activity: excessive, leading to rapid labor, as well as weak or discoordinated labor activity. In case of placental insufficiency or early aging placenta, fetal hypoxia of varying severity may occur. Such births must be carried out under cardiac monitoring (CTG).
Premature birth often has complications in the form of rupture of the membranes, which leads to early rupture of water. Amniotic fluid protects the fetus from various infections and injuries, and also plays a vital role in metabolism. Therefore, it is important to detect ruptured membranes in a timely manner. When clear discharge from the vagina, you should consult a doctor. It is quite difficult to diagnose such a complication, since the cervix is not fully dilated; therefore, it is almost impossible to determine the integrity of the bladder by visual examination. In this case, special tests may be carried out to determine water leakage. Ultrasound and analysis of vaginal discharge are also used to make a diagnosis.
If the membranes rupture early and there is no active labor for less than 34 weeks, the woman is under close medical supervision. After all, every hour spent in the mother’s womb increases the baby’s vitality. The expectant mother must undergo a series of tests every day and undergo special therapy that stimulates the maturation of the fetus’s lungs. At the first symptoms of inflammation of the amniotic membranes, labor is stimulated, otherwise not only the life of the child, but also the woman in labor itself is endangered.
How to avoid early labor?
If labor has already begun, it is unlikely to be stopped. Therefore, women who are found to be at risk of premature birth are placed in a hospital. Doctors determine the cause of miscarriage, determine the baby’s weight, and conduct a series of tests for possible infections. Physical and emotional peace is very important for the expectant mother, so pregnant women are often prescribed medications with a sedative effect (tincture of valerian or motherwort). Antispasmodics that have a relaxing effect on the uterus (Baralgin, No-shpa) can also be used.
In addition, therapy is aimed at eliminating the disease that causes early labor. Thus, in case of isthmic-cervical insufficiency, sutures can be placed on the cervix, but in more late dates(after 20 weeks) an obstetric pessary is usually used - special ring, worn on the cervix. In case of fetal hypoxia caused by placental insufficiency, special medications and vitamins are used, and if a source of infection is identified, a course of antibiotics is prescribed.
It is extremely important to think about how to avoid premature birth even before pregnancy. And here prevention and timely preparation are necessary. First of all, before conception, you should conduct an examination of the body, and if any violations are detected, go for a full course of treatment. A pregnant woman should monitor her diet, avoid emotional turmoil, see a gynecologist and take necessary tests. If there is a risk of premature birth, then during critical periods (2-3, 4-12 and 18-22 weeks) hospitalization in a maternity hospital is recommended. When the expectant mother is healthy and the pregnancy proceeds without pathologies, it is unlikely that she will experience premature labor.
Useful video information
Our article covers the causes, mechanism of development of premature birth, provoking factors, how to recognize the signs of premature birth, what diagnostic methods?
With the onset of pregnancy, most expectant mothers are overcome by numerous fears. One of them is the likelihood of spontaneous premature birth. In addition, the statistics are not reassuring: about 15 million premature babies are born every year in the world - approximately 10% of all live births.
Moreover, about 65% of premature babies die from complications in the first four weeks of life. Moreover, every second surviving baby often suffers from various ailments in the future - for example, visual impairment or neurological diseases. Therefore, today the problem of premature birth is so urgent.
However (fortunately or unfortunately), the same provoking factors in some expectant mothers lead to a sudden premature onset of labor, while in others they do not. Why? To answer this question, let's take a look at the disturbing topic. Agree that knowing the “enemy” by sight, the likelihood of avoiding undesirable developments is much higher.
Premature babies: new criteria
Premature birth is considered to occur between 22 and 37 weeks of pregnancy. In this case, the child’s weight ranges from 500 to 2500 grams, height – from 25 to 40 cm.
Development mechanism: spontaneous premature birth, how does it happen?
There are many factors that can trigger premature onset of labor. However, today there is no consensus on the list of factors under the influence of which the mechanism of premature birth is triggered.
And yet scientists have identified two main theories, which explain how the birth process starts long before the expected date.
Hormonal theory - when oxytocin “rebels”
Under the influence of provoking factors, the level of progesterone (pregnancy hormone) decreases and the content of estrogen (female sex hormones) increases. This imbalance leads to increased oxytocin production- a hormone that stimulates contraction of the muscles of the uterus.
Decidual theory - a “gap” in protection and nutrition
With the onset of pregnancy, the decidua or tissue that participates in the formation of the placenta is formed from the cells of the uterine mucosa. Normally, decidual tissue leaves after childbirth following the placenta.
However, in some cases, the composition of the uterine mucosa and the decidua itself changes much earlier, which leads to a deterioration in uterine and placental blood flow. As a result all functions of the placenta are disrupted: the production of hormones (primarily progesterone), providing nutrients and oxygen to the fetus, as well as protecting it from toxins and pathogens.
There is usually no clear distinction between the two mechanisms in practice. Since, as a rule, under the influence of provoking factors, both of them are involved in triggering changes that activate the contractile activity of the uterus.
Provoking factors: when the fetus is in danger
Conditions that can initiate premature onset of labor are somewhat better studied and systematized than the mechanisms of its development.
Groups of provoking factors for spontaneous preterm birth
The first group is maternal factors
Common reasons
1. Previous pregnancies ended in miscarriage or premature birth - evidence that a woman has a predisposition to miscarriage.
For example, with hereditary thrombophilia, there is a genetic tendency to form blood clots in the lumen of all vessels. What are the dangers of this during pregnancy? Blood clots formed in the lumen of the blood vessels of the placenta and uterus impair their nutrition, which is why mechanisms for the development of premature birth are triggered.
2. Incorrect “device” of the uterus- for example, underdevelopment (“baby uterus”) or developmental anomalies (bicornuate, septate, unicornuate, saddle-shaped). With these deviations, as the fetus grows, the space in the uterine cavity decreases, and its walls become overstretched.
3. Conducted in the past surgical operations on the cervix, or injury to her muscles during curettage (diagnostic or abortion). Such manipulations subsequently often lead to weakness of the muscle ring of the cervix.
Most common reasons related to current pregnancy
1. Mother's age
If the expectant mother under 18 years old, then her body is not ready for pregnancy and bearing a baby.
ABOUT early birth read our articles and
When the expectant mother over 35 years old, then she no longer has such good physical fitness. Moreover, with age, many mothers develop health problems: diabetes, thyroid diseases and others.
2.The interval between this pregnancy and the previous one is less than six months, therefore, the mother’s body does not have time to recover.
3. Large fetus, multiple pregnancies and polyhydramnios lead to overstretching of the uterine walls as the fetus grows.
4. Any genitourinary infections. Particularly dangerous are colpitis, which is caused by mycoplasma, ureaplasma, chlamydia and yeast fungus. Since these pathogens are able to penetrate from the vagina into the uterine cavity, and then infect the membranes of the fetus (with subsequent rupture) and amniotic fluid.
5. Premature rupture of membranes triggers mechanisms that enhance the production of oxytocin.
6. Any injuries, bruises and falls from height can lead to premature rupture of membranes and harm the fetus.
7. Cervical insufficiency develops due to the weakness of its muscles and connective tissue structures. Therefore, as the fetus grows, the internal os of the uterus opens, which facilitates the penetration of pathogenic microorganisms from the vagina into the uterine cavity. As a result, the amniotic membranes become infected (with subsequent rupture) and amniotic fluid.
8. Male sex of the fetus. According to statistics, slightly more premature boys are born than girls. Why? There is no clear answer to this question yet.
9. Increased uterine tone leads to increased contractions of her muscle fibers long before the expected date of birth.
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12. Preeclampsia occurs mainly in women with diseases: diabetes, pyelonephritis and others. Whereas healthy women are less susceptible to the formation of this erection.
With gestosis, a generalized (widespread) spasm of blood vessels occurs, and blood clots form in their lumen. Therefore, the work of all organs and systems of the mother’s body suffers. Under such conditions, the placenta cannot cope with its functions, which leads to the development of uteroplacental insufficiency and premature abruption of the normally located placenta.
13. Placenta previa- when the placenta completely or partially covers the internal os of the cervix. With this condition, the tone of the uterus often increases, which can trigger the onset of premature labor.
14. Smoking during pregnancy leads to the formation of microthrombi in the lumen of the placental vessels, therefore, blood flow in them is disrupted. As a result, conditions develop that provoke the onset of labor long before the expected term: premature rupture of membranes, placenta previa and premature abruption of a normally located placenta.
Stress increases cortisol production. What happens? The fact is that cortisol (stress hormone) and progesterone are formed from the same substance: 17-OH-progesterone. Therefore, in extreme conditions, all “raw materials” are spent on the production of cortisol. While there is nothing left for progesterone, which leads to a decrease in its level.
With great and powerful stress, changes occur quickly, with chronic stress - gradually.
The second group is fruit factors
In this case, Wise Nature gets rid of the obviously non-viable fetus, following one of its principles: “All or nothing.”
When is the natural “cordon” not passed?
There are two states:
1. Congenital anomalies of fetal development, which are incompatible with life:
* Congenital heart disease - for example, rearrangement of the main vessels of the heart (transposition).
* Absence of the anterior abdominal wall.
* Hydrocephalus (excessive accumulation of fluid in the brain) and others.
2. Chromosomal and genetic abnormalities - when changes occur in the chromosomes and genes of the parents, and then they are inherited by children. For example, Down syndrome, hemophilia (blood clotting disorder), cystic fibrosis and others.
However, premature birth usually occurs if the anomalies are gross. Whereas with unexpressed changes, as a rule, the child is born at term.
The third group is combined factors
Available incompatibility of the blood of mother and fetus by group or Rh factor. In this condition, the mechanisms of the immune system are activated, which cause disturbances in the “mother → placenta → fetus” system. As a result immune system The mother perceives the fetus as a “stranger” and therefore rejects it.
Premature birth: paradoxical situations
Of course, after reading the conditions described above, you can become seriously alarmed, even if the pregnancy is proceeding absolutely normally. Is it worth doing? Of course no. After all, our body is a self-regulating system, so it chooses what is best for it.
This is probably why it happens paradoxical situations:
* Available a large number of risk factors for premature birth. However, pregnancy and childbirth proceed absolutely normally, and the baby is born on time without any abnormalities.
* It would seem that, pregnancy is going well, but labor begins long before the expected date of birth.
What does this mean? Of course, the factors and mechanism of development of premature birth are not fully understood. Therefore, perhaps, you should not stress yourself out without obvious reasons, since stress will only aggravate the situation. It’s better to go through all the tests according to the timing of your pregnancy, and also follow your doctor’s orders.
Premature birth: how to recognize?
For some reason, there is a strong stereotype that the first signs of premature onset of labor are always pain in the lower abdomen and lumbar region. In fact, this option is only partly correct.
However, in 62% of women, such signs are not at all related to the state of pregnancy, but indicate an exacerbation or the occurrence of some disease in the woman. What to do? First of all, it is necessary to exclude diseases of the intestines, kidneys and bladder by visiting a doctor.
So, are you at risk? Then check out some of the signs that labor is starting well before the expected date.
“Shapes” of premature birth
First option
With the onset of premature labor, cramping pain appears, which occurs at a certain interval of time. However, they may be accompanied by minor bloody discharge and/or rupture of amniotic fluid.
Second option
Bloody discharge appears first, and pain comes a little later.
Third option
Premature rupture of the membranes and rupture of amniotic fluid occurs. At the beginning there are no pains, but they appear after a few hours or even days.
The condition is dangerous because when the membranes rupture prematurely, a large amount of water does not always leak out. Sometimes a small rupture occurs, so the amniotic fluid leaks out literally drop by drop. Such a mild symptom often misleads the expectant mother: she may think that the discharge has simply increased. As a result, valuable time is wasted.
As you can see, there are no signs by which we can say with 100% certainty that premature labor has begun.
However, medical studies are being conducted that confirm or refute the onset of labor long before the expected date.
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Methods for diagnosing preterm birth
Ultrasound: diagnostic criteria
In Russia Ultrasound is the only publicly available and widely used method, which allows you to determine the threat of premature birth. At the same time through the vagina The length of the cervix is examined: 3 cm or more means a normal pregnancy, less than 3 cm means a risk of premature birth.
Test systems: determining the risk of premature birth
For diagnostics premature rupture of amniotic fluid tests are used that determine rupture of the membranes and leakage of amniotic fluid. If this condition is detected in a timely manner, doctors are often able to keep the pregnancy as long as possible. possible deadline. This tactic allows you to prepare your baby for birth, as well as increase his chances of being born healthy.
In addition, the risk of preterm birth can be determined using detection of fibronectin in the vagina- a protein that is produced by chorion cells (part of the placenta). Normally, it appears in the vaginal contents only before childbirth. Early detection of fibronectin - high risk evidence premature birth within the next 14 days.
Unfortunately, the fibronectin test is not yet available in Russia. Therefore, in the vagina most often insulin-like factor is detected using the Actim-Partus test strip. This method less sensitive, but it allows you to predict the risk of preterm birth over the next seven days.
Knowledge about the mechanisms and risk factors of preterm birth: why is this necessary?
Of course, it is not always possible to prevent the birth of a premature baby, even with all the necessary information. In addition, much depends on the specific situation at hand.
However, statistics show that it is possible avoid premature birth.
For example, according to 10 research centers, 50% seem to have healthy women labor occurs spontaneously and unexpectedly long before the expected date.
Whereas women at risk for premature births, up to 75% of cases give birth on time. Because they are regularly monitored and receive the necessary medical care.
So, despite all the precautions, you have a premature baby? Don't despair, because modern conditions Even extremely low weight babies are nursed. True, success largely depends on the degree of prematurity and nursing conditions. This is exactly what we will talk about in the following materials.
resident doctor of the children's department
From the moment pregnancy begins, many women listen carefully to their bodies, fearing miscarriage or premature birth. Of course, such anxiety should not be excessive, because it can greatly fray the nerves to the expectant mother. But a normal, attentive attitude towards your body and your growing baby is really necessary. After all, the risk of premature birth is present in many pregnant women, so let’s clarify the signs of premature birth at 28 weeks.
Risk of giving birth before term
Doctors say that premature birth can happen to any pregnant woman if a number of factors contribute to it. However, for some expectant mothers, the likelihood of such a pregnancy outcome is an order of magnitude higher than for others.
As practice shows, the most common cause of premature birth is infection. After all, the uterine cavity is normally sterile, and inflammatory processes disrupt the normal structure of its walls in general, and the muscle layer in particular. It is for this reason that expectant mothers are strongly advised not to refuse to undergo examinations for the presence of various infections. And ideally, you should go through them at the stage of planning conception.
Particular care should be taken in this case by those representatives of the fair sex who have already encountered chronic and acute inflammatory lesions of the appendages, uterus or endometrium, with intrauterine interventions (abortions or diagnostic curettages). Also at risk are girls who have a history of spontaneous abortion.
The second most common cause of premature birth is considered isthmic-cervical insufficiency - the presence of inferiority of the muscular layer of the uterine cervix, which, when healthy pregnancy performs the function of a kind of retaining ring, preventing the expulsion of the embryo. This pathology can be congenital (which is extremely rare) or acquired. The likelihood of isthmic-cervical insufficiency increases with injuries to the isthmus and uterine cervix during abortion and previous births (for example, at birth large child, application of obstetric forceps, etc.). Also dangerous are the diagnostic manipulations carried out, during which a violent and rather crude expansion of the area was carried out cervical canal. Isthmic-cervical insufficiency can also occur due to hormonal problems, for example, with an excessive amount of androgens in the female body, etc.
Among possible factors, increasing the risk of premature birth, it is worth highlighting various pathologies in the activity of the endocrine glands, represented by the thyroid gland, adrenal glands, ovaries, and pituitary gland. Typically, such violations are not obvious and do not particularly affect the patient’s well-being.
Sometimes the role of a provoking factor in premature birth is played by overdistension of the uterus, for example, with multiple pregnancy, polyhydramnios and large fetal size.
Pathologists of uterine development (congenital), including infantilism, as well as a saddle-shaped or bicornuate uterus, can also play a role.
A number of other reasons, represented by severe physical work, any acute infectious diseases (especially with an increase in body temperature), severe and chronic stress, both at home and at work. The provoking factor may also be insufficient healthy image life: overwork, bad habits, etc.
Also, statistics show that if a woman already has a history of premature birth, the chance that new pregnancy the situation will repeat itself. Therefore, in this case, doctors may insist on hospitalization until date “X” in order to prevent possible start labor activity.
If you are at risk for preterm labor, don't panic. Simply inform your doctor of your concerns and follow their recommendations completely. In addition, try to eliminate the influence of all negative factors that depend on you.
How to recognize the approach of premature labor at 28 weeks of pregnancy?
In fact, preterm labor can be stopped if it gets into the hands of specialists before it reaches the stage of active labor.
Signs of labor
So, if a pregnant woman is bothered pulling sensations in the lower abdomen and lower back or even minor pain, you should carefully listen to your body and consult a doctor. The possibility of premature birth is also indicated by a parallel increase in the tone of the uterus, as a result of which the abdomen noticeably hardens. At the same time, the baby in the stomach can show unprecedented activity or, on the contrary, calm down for a long time. The appearance of mucous discharge, sometimes mixed with blood, may also occur. This is a serious reason to immediately call an ambulance.
If the pulling sensations intensify and become cramping in nature, it is better not to hesitate at all, and immediately call the doctors. At this stage, early birth can sometimes be avoided. Timely signs noticed at 28 weeks and timely referral to antenatal clinic will help maintain the correct course of pregnancy. If you have any doubts, go to the doctor immediately!
It is worth noting that modern development medicine allows the birth of babies born at 28 weeks of pregnancy. And in the absence of serious pathologies, they can fully catch up with their peers in development.
Its practical significance is due to the fairly high incidence of preterm birth in the population (up to 5-10%), the tendency to increase the frequency of preterm birth, and the high frequency of perinatal mortality in preterm birth.
The authors recommended testing using this scale during the first visit to the doctor and again at 22-26 weeks of pregnancy. In the case of a total score of 10 or more, the patient is classified as a high-risk group for the development of spontaneous preterm birth.
The disadvantages of this scale are caused primarily by how long ago it appeared - it does not take into account such significant factors in modern obstetrics as induction
Risk of premature birth
table 2
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pregnancy, IVF, presence of genital viral infection, laparoscopic surgical interventions in the anamnesis, which, however, does not reduce its high practical significance.
Screening for the first trimester of pregnancy is over, time passes, the belly grows, and new worries arise.
Have you heard or read somewhere about isthmic-cervical insufficiency (ICI), premature birth, ultrasound of the cervix and now you don’t know whether this threatens you and whether you need such a study, and if necessary, when?
In this article I will try to talk about such a pathology as ICN, about modern methods its diagnosis, the formation of a high-risk group for premature birth and treatment methods.
Premature birth is defined as birth that occurs during pregnancy from 22 to 37 weeks (259 days), starting from the first day of the last normal menstruation with regular menstrual cycle, while the fetal body weight ranges from 500 to 2500 g.
The frequency of preterm births in the world in last years is 5–10% and, despite the emergence of new technologies, is not decreasing. And in developed countries it increases, first of all, as a result of the use of new reproductive technologies.
Approximately 15% of pregnant women are at high risk for premature birth even at the stage of collecting anamnesis. These are women who have a history of late miscarriages or spontaneous premature birth. There are about 3% of such pregnant women in the population. In these women, the risk of recurrence is inversely related to the gestational age of the previous preterm birth, i.e. The earlier the premature birth occurred in the previous pregnancy, the higher the risk of recurrence. In addition, this group may include women with uterine anomalies, such as a unicornuate uterus, a septum in the uterine cavity, or injuries surgical treatment cervix.
The problem is that 85% of preterm births occur in 97% of women in the population for whom this is their first pregnancy, or whose previous pregnancies resulted in full-term births. Therefore, any strategy aimed at reducing the rate of preterm birth that targets only a group of women with a history of preterm birth will have very little impact on the overall rate of preterm birth.
The cervix plays a very important role in maintaining pregnancy and the normal course of labor. Its main task is to serve as a barrier that protects the fetus from being pushed out of the uterine cavity. In addition, the glands of the endocervix secrete special mucus, which, when accumulated, forms a mucus plug - a reliable biochemical barrier to microorganisms.
“Cervical ripening” is a term used to describe the rather complex changes that occur in the cervix related to the properties of the extracellular matrix and the amount of collagen. The result of these changes is the softening of the cervix, its shortening to the point of smoothing, and the expansion of the cervical canal. All these processes are normal during full-term pregnancy and are necessary for the normal course of labor.
For some pregnant women, due to various reasons“Cervical ripening” occurs ahead of time. The barrier function of the cervix is sharply reduced, which can lead to premature birth. It is worth noting that this process does not have clinical manifestations, is not accompanied by pain or bleeding from the genital tract.
What is ICN?
Various authors have proposed a number of definitions for this condition. The most common is this: ICI is an insufficiency of the isthmus and cervix, leading to premature birth in the second or third trimester of pregnancy.
or something like that : ICI is a painless dilatation of the cervix in the absence of
uterine contractions, leading to spontaneous interruption
pregnancy.
But the diagnosis must be made even before the termination of pregnancy occurs, and we don’t know whether it will happen. Moreover, most pregnant women diagnosed with ICI will deliver at term.
In my opinion, ICI is a condition of the cervix in which the risk of preterm birth in a given pregnant woman is higher than the general population.
In modern medicine, the most reliable way to assess the cervix is transvaginal ultrasound with cervicometry - measuring the length of the closed part of the cervix.
Who is indicated for cervical ultrasound and how many times?
Here are the recommendations from https://www.fetalmedicine.org/ The Fetal Medicine Foundation:
If a pregnant woman is among those 15% with a high risk of preterm birth, then such women are shown an ultrasound of the cervix every 2 weeks from the 14th to the 24th week of pregnancy.
For all other pregnant women, a single ultrasound of the cervix is recommended at 20-24 weeks of pregnancy.
Cervicometry technique
Woman empties bladder and lies on the back with bent knees (lithotomy position).
The ultrasound probe is carefully inserted into the vagina towards the anterior fornix so as not to place excessive pressure on the cervix, which could artificially increase the length.
A sagittal view of the cervix is obtained. The mucous membrane of the endocervix (which can be either increased or decreased echogenicity compared to the cervix) serves as a good guide to determine the true position of the internal os and helps to avoid confusion with the lower segment of the uterus.
The closed part of the cervix is measured from the external os to the V-shaped notch of the internal os.
The cervix is often curved and in these cases the length of the cervix, considered as a straight line between the internal and external os, is inevitably shorter than the measurement taken along the cervical canal. From a clinical point of view, the measurement method is not important, because when the cervix is short, it is always straight.
Each test should be completed within 2-3 minutes. In about 1% of cases, the length of the cervix may change depending on uterine contractions. In such cases, the lowest values should be recorded. In addition, the length of the cervix in the second trimester may vary depending on the position of the fetus - closer to the fundus of the uterus or in the lower segment, in a transverse position.
You can evaluate the cervix transabdominally (through the abdomen), but this is a visual assessment, not cervicometry. The length of the cervix with transabdominal and transvaginal access differs significantly by more than 0.5 cm, both up and down.
Interpretation of research results
If the length of the cervix is more than 30 mm, then the risk of premature birth is less than 1% and does not exceed the general population. Such women are not indicated for hospitalization, even in the presence of subjective clinical data: pain in the uterus and minor changes in the cervix, heavy vaginal discharge.
- If a shortening of the cervix of less than 15 mm is detected in a singleton pregnancy or 25 mm in a multiple pregnancy, urgent hospitalization and further management of the pregnancy in a hospital with the possibility of intensive care for newborns are indicated. The probability of delivery within 7 days in this case is 30%, and the probability of premature birth before 32 weeks of pregnancy is 50%.
- Shortening of the cervix to 30-25 mm during a singleton pregnancy is an indication for consultation with an obstetrician-gynecologist and weekly ultrasound control.
- If the length of the cervix is less than 25 mm, a conclusion is issued: “ECHO signs of ICI” in the 2nd trimester, or: “Given the length of the closed part of the cervix, the risk of premature birth is high” in the 3rd trimester, and a consultation with an obstetrician-gynecologist is recommended for deciding whether to prescribe micronized progesterone, perform cervical cerclage or install an obstetric pessary.
A few words about the opening and shape of the internal pharynx. When performing an ultrasound of the cervix, you can find various shapes internal os: T, U, V, Y - shaped, moreover, it changes in the same woman throughout pregnancy.
With ICI, along with shortening and softening of the cervix, its dilatation occurs, i.e. expansion of the cervical canal, opening and changing the shape of the internal os is one process.
A large multicenter study conducted by FMF showed that the shape of the internal os itself, without shortening the cervix, does not statistically increase the likelihood of preterm birth.
Treatment options
Two methods of preventing premature birth have been proven effective:
- Cervical cerclage (suturing the cervix) reduces the risk of labor before 34 weeks by about 25% in women with a history of preterm labor. There are two approaches to treating patients with previous preterm birth. The first is to perform cerclage on all such women shortly after 11-13 weeks. The second is to measure the length of the cervix every two weeks from 14 to 24 weeks, and apply sutures only if the length of the cervix becomes less than 25 mm. General indicator Premature birth rates are similar for both approaches, but the second approach is preferred because it reduces the need for cerclage by approximately 50%.
Randomized studies have shown that in the case of multiple pregnancies, when the cervix is shortened to 25 mm, cervical cerclage doubles the risk of preterm birth.
- Prescribing Progesterone from 20 to 34 weeks reduces the risk of childbirth before 34 weeks by approximately 25% in women with a history of premature birth, and by 45% in women with an uncomplicated history, but identified shortening of the cervix to 15 mm. A study was recently completed that showed that the only progesterone that can be used for a short cervix is micronized vaginal progesterone at a dose of 200 mg per day.
- Multicenter studies of the effectiveness of using a vaginal pessary are currently ongoing. A pessary, which consists of flexible silicone, is used to support the cervix and change its direction towards the sacrum. This reduces the strain on the cervix due to reduced pressure ovum. You can read more about the obstetric pessary, as well as the results of the latest research in this area
After suturing the cervix or with an obstetric pessary in place, ultrasound of the cervix is not advisable.
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