Oligohydramnios during pregnancy: causes and consequences, dangers, treatment

General information

What is oligohydramnios in pregnancy (medical term oligohydramnios)?
This is a pathological condition in which the amount of amniotic fluid decreases (less than 500 ml) while the membranes are intact and without signs of water leakage. Amniotic fluid (synonymous with amniotic fluid) surrounds the fetus and is the medium that connects it and the mother’s body. Their main function is to ensure the vital activity of the fetus, nutrition and its development, protection from infections and injuries, and facilitating the movements of the developing fetus. The circulation of amniotic fluid is a training factor for the fetal excretory and respiratory system. Oligohydramnios is regarded as a manifestation of pregnancy , which subsequently affects its outcome. It indirectly indicates congenital anomalies, the presence of intrauterine infection and even fetal death, leading to complications of pregnancy and childbirth, which is why it is an urgent problem in obstetrics. We can say that insufficient amniotic fluid is a woman’s body’s response to any changes in her health or the fetus, which may be associated with infections or endocrine pathology. However, only a decrease in water levels below normal without changes in ultrasound, Dopplerography and cardiotocography is not considered as a marker of fetal pathology. Quite often (20-50% of cases) idiopathic oligohydramnios , when no pathology is detected in the woman or the fetus.

Amniotic fluid appears in the third week and normally its volume changes with the duration of pregnancy: at 10 weeks it is 30 ml, then gradually increases and by 37-38 weeks it reaches 1500 ml, and by the end of the period it decreases again. Typically, at the end of pregnancy, moderate oligohydramnios is physiological and does not pose a danger. Most of the water is secreted by the amniotic sac (part of the placenta); the fetus also secretes up to 500 ml of liquid during its life. If the pregnant woman is healthy, then the placenta produces a normal amount of amniotic fluid for the duration of pregnancy. Its normal volume is an indicator of the proper functioning of the membranes and the fetal urinary system. This pathology can appear in any trimester, but more often develops in the third trimester (by 37-38 weeks), which is associated with the aging of the placenta and a decrease in its function. There are cases of the development of oligohydramnios before the 20th week.

Etiology and pathogenesis

The etiology and pathogenesis are not clear enough. Oligohydramnios is usually explained by insufficient development of the epithelium lining the aqueous membrane or a decrease in its secretory function. In most cases, oligohydramnios develops during post-term pregnancy; It is often observed in one of the identical twins with polyhydramnios in the other, which is explained by the uneven distribution of blood circulating in the common placenta. There are indications in the literature about the gradual disappearance of amniotic fluid, which was initially present in normal quantities.

Pathogenesis

The production of amniotic fluid and the maintenance of its volume is a process of formation and absorption that occurs constantly. This process involves the fetal membranes, umbilical cord epithelium, surface of the placenta, lungs, fetal intestines and its urinary system. Up to 5 weeks, water is produced by the chorion , then by the amniotic membrane ; starting from the second trimester, the kidneys (urine) and lungs of the fetus (alveolar fluid) take over the function. The main source of fluid is urine. During a full-term pregnancy, the fetus secretes from 400 to 1200 ml of urine. The lungs of a full-term baby secrete 300–400 ml per day. Amniotic fluid is renewed every three hours, the change of dissolved substances occurs within 5 days.

The volume of liquid is affected by:

Fetal urination is the main source in the 2nd half of pregnancy, if there are kidney abnormalities, very little amniotic fluid is formed. In a normal full-term pregnancy, the fetus produces 700-900 ml of urine per day.
Ingestion of water by the fetus. At full term, he swallows 230-750 ml per day.
Secretion of fluid by the lungs.
The developed lack of amniotic fluid affects the child - his skin becomes wrinkled and dry, he begins to lag in growth. The walls of the uterus compress it because they fit tightly to the fetal sac, and the fetus itself comes into contact with the amnion. As a result of close contact with the amnion, cords (Simonartian ligaments or constrictions) are formed between the inner surface of the amnion and the fetus. Strands can cause defects or amputation of fingers and, in some cases, amputation of limbs. Club feet and spinal curvature also develop . If Simonart's ligaments compress the umbilical vessels, death occurs.

Definition of concept and norm

Moderate oligohydramnios during pregnancy is when the volume of amniotic fluid is slightly lower than necessary. This condition is most often easily corrected. With the help of modern equipment, the emerging problem can be diagnosed during the 2-3 trimester. Most often, this pathology is called an implicit deviation.

At different stages of gestation there are different indicators of the volume of amniotic fluid. In the first month and a half they are only 5 ml. Then there is a constant increase in their volume, and already a few weeks before the birth of the baby it can vary from 1 to 1.5 liters. Immediately before the birth itself, the water level becomes smaller: about 600 ml.

Intrauterine fluid is constantly renewed. In the last stages of gestation, these processes occur every three hours. The baby swallows approximately 4 liters of water per day. Its waste products are excreted through special channels and pores of the amnion. This liquid is obtained during the work of the epithelium of the aqueous membrane.

If there are minor deviations from the norm to a lesser extent, then this condition is defined as moderate oligohydramnios during pregnancy. The treatment and consequences of this disease can be different, so the problem requires constant monitoring by specialists, and then the prescription of medication correction.

Classification

Forms of polyhydramnios:

Early, developing from 16 to 20 weeks and associated with inadequate function of the membranes. May indicate fetal developmental abnormalities.
Later, detected in the II-III trimester (after 26 weeks). This form develops against the background of maternal diseases, pathology of the placenta and pathology of pregnancy. It may also be caused by partial prenatal rupture of the membranes.

By duration:

Chronic - forms slowly and progresses. To confirm it, ultrasound and other studies are carried out over a period of 1-2 months. With progression, a final diagnosis is made.
Acute (transient) - occurs acutely and temporarily, develops after a respiratory infection , sore throat or poisoning . This form is benign and disappears after the pregnant woman recovers.

By severity:

Mild severity (IAP - amniotic fluid index 5-10 cm).
Moderate severity (amniotic fluid index 2-5 cm).
Severe (IAP less than 2 cm).

Moderate oligohydramnios during pregnancy (amniotic fluid is determined in the amount of 400-500 ml) is detected by chance on an ultrasound scan, since moderate oligohydramnios is not accompanied by any objective symptoms. Severe oligohydramnios is diagnosed if the lack of fluid exceeds 700 ml. Severe oligohydramnios is already accompanied by symptoms - pain when the fetus moves, dizziness , nausea or vomiting, and there may be dry mucous membranes.

How does oligohydramnios affect the development of pregnancy and the condition of the fetus? In any trimester, it is associated with risks for the pregnant woman and the fetus. Oligohydramnios during pregnancy 20 weeks is often associated with fetal death. The prolonged presence of oligohydramnios during this period increases the risk of chest abnormalities, underdevelopment of the pulmonary artery and limb deformities. Typically, in this period, oligohydramnios develops after infectious and inflammatory diseases and is combined with placental insufficiency and developmental abnormalities. Pregnant women have a history of cytomegalovirus infection , herpes infection or parainfluenza . If oligohydramnios, inflammation of the placenta and membranes, and embryogenesis disorders are detected, the question of the advisability of continuing the pregnancy is decided.

If oligohydramnios is detected at 32 weeks of pregnancy, it is prolonged. Moderate oligohydramnios at this stage is not dangerous, but to clarify the condition of the fetus, cardiotocography is performed at 32-33 weeks of gestation and monthly ultrasound monitoring. In cases of severe oligohydramnios and increased uterine tone, hospitalization is indicated at 34 weeks. Treatment includes sedatives, antispasmodics, drugs that improve placental blood flow, and, if indicated, hormones . The efforts of doctors are aimed at prolonging pregnancy and maturing the baby, so the pregnant woman is offered hospitalization in order to maintain the pregnancy.

At 36 weeks - 37, the fetus continues to be actively monitored, treatment is prescribed to improve metabolism in the placenta and gas exchange, as well as vitamins. For hypertension, tocolytics are prescribed. If conservative treatment does not produce results, the amount of amniotic fluid continues to decrease, and the condition of the fetus worsens, delivery is recommended regardless of the gestational age. Given the high risk of complications during childbirth, preference is given to caesarean section.

38 or 39 weeks is the period at which a pregnant woman can give birth, so a planned caesarean section . Oligohydramnios at 40 weeks and 41 is associated with post-term pregnancy, since by 40 weeks the amount of water normally decreases to 0.6 l - this is an indication for delivery.

“Habitat”: amniotic sac and amniotic fluid

Throughout pregnancy, the baby's living space is limited to the uterine cavity. In addition to the fetus itself, the uterus contains the membranes and placenta - the so-called pregnancy organs. These organs actually appear and function in the body of the expectant mother only during pregnancy; After the baby is born, they are separated from the wall of the uterus and are born in the form of an afterbirth.

The main function of the membranes is to create and maintain normal conditions for the baby’s intrauterine life. The amnion plays a significant role in ensuring an optimal microclimate for the fetus.

The amnion, or membrane of water, is a closed sac that contains the fetus, surrounded by water. The aqueous membrane fits tightly to the inner surface of the uterine wall, lines the inner surface of the placenta and passes to the umbilical cord, covering it in the form of a sheath. In the area of the baby's navel, the membrane passes onto the skin of the tummy, gradually merging with it.

The amniotic sac (amnion) consists of a thin membrane in which two layers are distinguished. The inner layer - epithelial - faces the fetus. The outer layer is called connective tissue and is closely adjacent to the wall of the uterus. The amniotic sac is thin, but dense and very elastic. Its surface is transparent, smooth and slightly shiny.

During pregnancy, the walls of the amniotic sac produce a special fluid - amniotic fluid. Normally, the amount of water at the end of pregnancy ranges from 800 to 1500 ml. The composition of amniotic fluid, or amniotic fluid, includes protein, various salts, urea, carbohydrates (sugar) and hormones (folliculin, gonadotropic hormone) necessary for normal metabolism and fetal development. In the first half of pregnancy, the fetal fluid is clear and clean. In the second half, and especially towards the end of pregnancy, the waters become somewhat cloudy. This turbidity depends on fetal elements mixed with the amniotic fluid. These elements include:

lanugo is the name given to the delicate hairs that cover the baby’s skin during a certain period of embryonic development;
vernix - fatty lumps that cover the skin of the fetus in the form of a curdled or cheese-like mass and protect it from maceration (wrinkling and damage to the skin from constant exposure to a liquid medium);
desquamated epidermis - scales of dead fetal skin cells

The composition of amniotic fluid is controlled by the walls of the fetal bladder: the fetal bladder is penetrated by the finest blood vessels, from the plasma of which amniotic fluid is formed. Amniotic fluid is constantly renewed; A complete change in the composition of water normally occurs in about three days.

The physiological significance of amniotic fluid in the development of pregnancy and the fetus is enormous.

The amount of amniotic fluid gradually increases as pregnancy progresses. In the first months there is relatively a lot of water, and the baby can move freely, “swim” in his water container. Towards the end of pregnancy, the amount of water increases, stretching the walls of the uterus, but at the same time the fetus grows significantly, and it grows quite quickly. In the third trimester, the fetus already occupies almost the entire uterine cavity, the baby’s movements are limited: he cannot, as before, constantly change his position and position in the uterus.

The physiological significance of amniotic fluid in the development of pregnancy and the fetus is enormous. The waters create a unique habitat for the baby. They prevent the formation of adhesions between the amnion and the skin of the fetus. Amniotic fluid creates the opportunity for unimpeded active movements of the baby, which are so necessary for its correct, normal development. At the same time, the waters protect the umbilical cord and placenta from pressure from large parts of the fetal body. Amnion and amniotic fluid protect the baby from shocks and bruises from the outside, make the baby’s movements less noticeable for the expectant mother, a normal amount of amniotic fluid ensures the formation of the correct position of the fetus in the uterus by the end of pregnancy. The amniotic sac, filled with water, participates in the process of dilation of the cervix in the first stage of labor: during contractions, the walls of the uterus compress, causing the elastic amniotic sac to “bulge” into the lumen of the cervix; the pressure of the amniotic sac on the cervix increases its dilatation.

Causes of oligohydramnios during pregnancy

In most cases, the cause of insufficient amniotic fluid is:

Underdevelopment of the amniotic epithelium, as a result of which the production of fluid in the required quantity is impaired.
Damage to the membranes due to infectious and inflammatory diseases: vulvovaginitis , adnexitis , endometritis . When oligohydramnios is detected in pregnant women, a history of chlamydia , trichomoniasis , HPV infection , mycoplasmosis , gonorrhea or syphilis is noted.
Extragenital pathology of women - chronic kidney disease, collagenosis , cardiovascular diseases.
Metabolic disorders in a pregnant woman ( obesity , diabetes mellitus ). Women with this pathology constitute a risk group, and insufficient production of amniotic fluid is noted from the first trimester.
Primary placental insufficiency associated with malformations or infarctions .
Abnormal attachment, premature detachment, premature aging of the placenta.
Anomalies in the development of the urinary system in the fetus ( polycystic kidney disease , underdevelopment of the kidneys, various types of atresias and obstructions of the urinary system).
Delayed fetal development or death, chromosomal pathologies (trisomy 13,21,18).
Post-term pregnancy, which is the cause in 20-30% of cases. The volume of fluid increases until 36-37 weeks, and then begins to decrease and goes to a minimum during post-term pregnancy.
Oligohydramnios is often observed in one of the twins if the other develops polyhydramnios at the same time. This is due to the fact that the blood circulating in the common placenta is distributed unevenly.
The use of non-steroidal anti-inflammatory drugs by a pregnant woman, which increases the risk of kidney pathology in the fetus. In this case, oligohydramnios can develop quickly (within two days of use) or within several weeks from the start of NSAID treatment. Usually this condition is reversible and disappears when the drug is discontinued.
In 25%, idiopathic oligohydramnios for no apparent reason.

In the first trimester, insufficient water supply is a rare finding, but is associated with an unfavorable prognosis (threat of miscarriage). The reasons for the development of this pathology during this period: heart abnormalities, chromosome number abnormalities, rupture of membranes and intrauterine fetal death. An iatrogenic cause—medical manipulation (chorionic villus biopsy)—cannot be ruled out.

Oligohydramnios in the second trimester is most often associated with obstruction , rupture of membranes, placental abruption and early fetal growth restriction. Sometimes it is possible to detect deviations in the amount of water only in the third trimester: in the prenatal period (37-38 weeks) oligohydramnios is detected in 3%-5% of cases, and in 40-41 weeks - in 5%-11%.

Causes of oligohydramnios in the 3rd trimester of pregnancy:

premature rupture of membranes;
intrauterine growth retardation;
placental abruption;
Iatrogenic causes (pregnant women taking ACE inhibitors or non-steroidal anti-inflammatory drugs).

What is the danger

The reasons why you need to see a doctor can be both minor and serious. Ailments that occur in the second trimester are of a different nature. In the middle of the cycle, the baby’s active growth occurs, and if the fluid decreases, the fetus begins to compress the walls of the uterus. In turn, this can lead to deformation of the skull bones, congenital hip dislocation and other abnormalities. These children are then monitored by an orthopedist. If you contact a specialist in a timely manner, these defects can be corrected.

It is important to understand the dangers of moderate oligohydramnios during pregnancy in the later stages. Causes and symptoms are also very different. At this stage, the woman undergoes the last ultrasound, based on the results of which the doctor determines the amount of amniotic fluid. During this period, the water begins to shrink on its own, but if there is much less of it than normal, then you need to pay special attention to this, because this factor can affect the course of labor. If there is even moderate oligohydramnios, this is often fraught with the premature birth of the baby. If a child is born at term, there is a possibility that this will affect the opening of the uterus, since it is the amniotic sac that presses on it at the time of delivery, due to which it opens.

Symptoms

Clinical signs of moderate oligohydramnios are not expressed and pathology can only be determined by ultrasound. Signs of severe oligohydramnios include:

poor fetal movement;
pain or discomfort when moving;
lower abdominal pain;
morning sickness and dry mouth;
restless sleep;
weakness and apathy;
spontaneous miscarriage.

Upon examination, the size of the uterus is insufficient in terms of time, its consistency is dense, the fetus is inactive and its position is incorrect.

Symptoms and clinical picture of oligohydramnios

The manifestations of the clinical picture do not specifically indicate signs of oligohydramnios. Most often, the presence of pathology is indicated by constant pain in the abdominal area, which increases during the period of fetal motor activity.

The most typical symptoms of oligohydramnios include:

discrepancy between the size of the abdomen and the indicators characteristic of a certain period;
a feeling of pain when the fetus moves in the second trimester of pregnancy;
discharge of fluid from the vagina (with rupture of the membranes).

Tests and diagnostics

An external obstetric examination is carried out - the abdominal circumference and the position of the fundus of the uterus are measured. Due to a decrease in amniotic fluid, these indicators are deviated downward, and fetal mobility is limited.
On vaginal examination, the uterus is toned and the amniotic sac is flat.
An important study is ultrasound assessment of amniotic fluid. The amniotic fluid index is calculated: the uterine cavity is mentally divided into 4 quadrants and the depth of the amniotic fluid pocket is determined in each. The sum of the values in the four quadrants is the amniotic fluid index. If the pocket depth is less than 2 cm and the index is less than 5 cm, then this indicates oligohydramnios.
Examination of a pregnant woman for the presence of infections (examination of urine, blood, smears for pathogenic flora, PCR testing for infections).
Assessment of the length of the cervical canal (determines the risk of premature birth).
Ultrasound of the fetus, which allows you to determine developmental anomalies.
Cardiltocography. Assess the condition of the fetus by its heartbeat. The study is carried out only in the third trimester (after 32 weeks).

Diagnosis of oligohydramnios

A pathological decrease in amniotic fluid is diagnosed during a routine ultrasound, on the basis of which the volume of water is calculated. To do this, several different techniques are used: measuring the vertical pocket and calculating the liquid index. When the volume of water decreases to a level of less than 550 ml, a diagnosis of pathological oligohydramnios is made.

To identify the main cause of the pathology, additional studies are prescribed: genetic screenings, laboratory tests, measurement of fetal heart rate.

Diagnostic methods

The following instrumental tests are mandatory: ultrasound diagnostics, measurement of abdominal circumference during a routine examination by a gynecologist.

Diet

Diet 15 table

Efficacy: therapeutic effect after 2 weeks
Timing: constantly
Cost of food: 1600-1800 rubles per week

It goes without saying that during pregnancy, a balanced and healthy diet with sufficient calories, vitamins and minerals, and protein is important. In this regard, a pregnant woman can adhere to dietary Table No. 15 , but increase the content of protein, foods rich in calcium, iron, zinc, omega-3 fatty acids (fatty fish, flaxseed oil, nuts). The positive effect of antioxidants and methionine in the normal development and functioning of the placenta has been proven. Methionine is found in Brazil nuts, milk, meat, fish, powdered eggs, Parmesan cheese, beans, red caviar, beans, almonds, lentils, sesame seeds, and soybeans.

A balanced diet for this pathology is more prevention than treatment, so from the first days of pregnancy a woman should reconsider her diet. Animal fats and simple carbohydrates (sweets, baked goods, confectionery) are significantly limited in the diet.

Prevention

Timely registration with a gynecologist and compliance with all doctor’s recommendations (rational nutrition, avoidance of stress and hard work at work).
Careful monitoring of pregnant women at risk - women with a history of oligohydramnios, urogenital infection, obesity and diabetes.
Prenatal diagnosis includes early detection of defects of the musculoskeletal and genitourinary systems.
In case of postterm pregnancy, urgent delivery is indicated.
The complex of measures for predicting oligohydramnios should include medical genetic consultation.
If oligohydramnios develops, a pregnant woman should avoid physical activity, eat right and visit a gynecologist.

Is it possible to prevent oligohydramnios?

Symptoms, causes, diagnosis, treatment are very important factors, but is it possible to predict the occurrence of a problem in advance and ensure that the woman remains healthy? Unfortunately, such preventive measures do not exist. But there are special rules, following which, you can minimize the development of a variety of pathologies. These include avoiding excessive physical activity and carrying heavy objects.

It is important to pass all tests and undergo timely examinations that help to exclude various ailments that can later cause oligohydramnios during pregnancy. The causes and consequences of past diseases are negative. Therefore, it is better to take measures in advance and undergo a course of treatment that will improve the health of both the expectant mother and the child.

To improve your well-being, you need to eat right. Doctors and nutritionists recommend eating smaller meals, eating food at least five times a day, but in small portions. This will have a beneficial effect on the health of both the woman and the baby.

Consequences of oligohydramnios during pregnancy and complications

Why is oligohydramnios dangerous? When considering the consequences, it is necessary to indicate the consequences for the mother and for the fetus. For a woman, oligohydramnios is dangerous:

threat of abortion;
premature birth;
anemia;
premature placental abruption;
preeclampsia;
weakness of labor;
bleeding.

This condition threatens the development of the fetus:

defects of the musculoskeletal system (congenital pathology of the feet, muscular torticollis , curvature of the spine, various bone deformities);
genitourinary system (bilateral renal underdevelopment, polycystic kidney disease );
congenital heart disease ;
chronic hypoxia ;
growth retardation.

Forecast

The prognosis for this pathology and the outcome of childbirth depend on the severity and time of development. An unfavorable prognosis for the fetus occurs with the development of oligohydramnios in the second trimester, since there is a possibility of the development of multiple anomalies and the possible death of the child. In this regard, it is important to resolve the issue of the possibility of prolonging pregnancy. Prolonging pregnancy is problematic with the development of oligohydramnios at the very beginning of the third trimester and developmental delay. If the condition of the fetus is normal and there is no growth retardation, then with oligohydramnios in the third trimester it is possible to carry the pregnancy to 37-38 weeks and have a favorable birth outcome.

Treatment of oligohydramnios

Both moderate and severe oligohydramnios are treated only as prescribed by a gynecologist. Self-medication in this case is unacceptable.

Before choosing individual therapy for a pregnant woman, the doctor must study the results of CTG and ultrasound to objectively assess the current condition of the child and the severity of the disease. It is necessary to find out the cause of this phenomenon in order to choose the most effective treatment method.

If there is excess weight and metabolic disorders in a woman’s body, the correct diet, medications that improve blood supply to the placenta and vitamins are prescribed.

Moderate oligohydramnios can be treated on an outpatient basis, but in severe forms the patient must be hospitalized.

In case of oligohydramnios, restriction of physical activity and reduction in the amount of physical activity are prescribed. To control the amount of amniotic fluid, an ultrasound of the pregnant woman’s abdominal cavity is performed somewhat more often to see the presence or absence of dynamics.

In the last stages of pregnancy, with severe oligohydramnios, a decision may be made about early birth.

If a woman already had oligohydramnios during a previous pregnancy, it is necessary to inform the gynecologist who is managing the pregnancy about this.

List of sources

Kaganova M. A, Spiridonova N. V. Analysis of the characteristics of the course of labor and perinatal outcomes in isolated oligohydramnios/Postgraduate Bulletin of the Volga Region. - 2022. - issue 5-6, pp. 39-43.
Sidorenko V.N., Bugrov V.Yu. Modern view on the etiopathogenesis of oligohydramnios and polyhydramnios, and ways to solve them for polyhydramnios of an infectious nature/Medical news. - 2022. - No. 4. pp. 53-57.
Voevodin S.M., Shemanaeva T.V., Serova A.V. Modern aspects of the diagnosis and pathogenesis of oligohydramnios/Gynecology. — 2022, VOLUME 19, No. 3
Alieva L.I., Alieva E.M., Mamedova S.N. Efficacy of complex pathogenetic therapy for pregnant women with oligohydramnios/Medical news. - 2022. - No. 1, pp. 77-79
Prytkov A.N., Zakharov L.V., Karkusova A.V. The occurrence of congenital malformations of the fetus with pathological content of amniotic fluid in the mother during pregnancy / Medical genetics. - 2004. - No. 11. — P.529-532.

Treatment

Treatment is aimed at eliminating the cause that caused the change in the amount of water. Complex therapy for feto-placental insufficiency is usually carried out, since it almost always occurs with both oligohydramnios and polyhydramnios.

If an infection is detected, antibiotic treatment is prescribed. With this pathology, antibiotic treatment can be prescribed even if no infection is detected (which often causes confusion among expectant mothers). The fact is that it is impossible to examine all existing microorganisms, and if the doctor does not see any other causes of polyhydramnios, treatment is carried out against infection, since this is the most common cause of polyhydramnios.

If fetal malformations incompatible with life are detected before 28 weeks, the woman is offered termination of pregnancy.

If other causes are identified (increased blood pressure in the mother, diabetes mellitus, Rh conflict, etc.), the underlying disease is treated.

An increase or decrease in fluid intake does not affect the amount of amniotic fluid.