Multihidus in pregnant women in late pregnancy: Ultrasound signs, management of labor

Polyhydramnios (hydramnion) is a condition characterized by excessive accumulation of amniotic fluid in the amniotic cavity. With polyhydramnios, the amount of amniotic fluid exceeds 1.5 liters and can reach 2-5 liters, and sometimes 10-12 liters or more. According to various authors, this pathology occurs in 0.6-1.7% of pregnant women.

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Causes of polyhydramnios

Pathological conditions of pregnancy in which polyhydramnios may occur:

• diabetes mellitus;
• acute or chronic infections, in particular TORCH infections;
• inflammatory processes of the female genital organs;
• multiple pregnancy;
• isoserological incompatibility of the blood of the mother and fetus, most often according to the Rh factor;
• gestosis;
• cardiovascular diseases;
• anemia;
• hemoglobinopathy (α-thalassemia);
• fetal developmental abnormalities;
• placental pathology (chorionangioma).

Among the causes of polyhydramnios, diabetes mellitus occupies one of the leading places - 25%.

The direct etiological factor of polyhydramnios is also infection. It has been proven that signs of inflammation of the tissues of the placenta and fetal membranes are present in 50% of cases of polyhydramnios.

The frequency of congenital defects of the fetus in polyhydramnios, according to different authors, fluctuates within fairly wide ranges and is no less than 20%.

The most common congenital malformations with polyhydramnios are those of the central nervous system (anencephaly, hydrocephalus, microcephaly, spina bifida, etc.) and the digestive tract (esophageal atresia, atresia of the duodenum, colon, Hirschsprung's disease, Meckel's diverticulum, diaphragmatic hernia, omphalocele, gastroschisis, etc.).

It is known that the following mechanisms underlie the development of polyhydramnios:

• hyperproduction of amniotic fluid components by the amnion epithelium and delayed removal of them (TORCH infections, inflammatory processes of the female genital organs);
• excessive transudation through fetal vessels, which is observed in the recipient fetus in transfusion syndrome in the case of multiple pregnancies or in the case of widespread placental hemangioma;
• disruption or absence of the mechanism of swallowing amniotic fluid by the fetus as one of the mechanisms regulating its quantity (congenital defects of the fetal digestive tract);
• additional transudation of fluid through large skin defects of the fetus (ulcerative teratoma and other fetal malformations).

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Symptoms of polyhydramnios

A distinction is made between acute and chronic polyhydramnios. Chronic polyhydramnios develops gradually and the pregnant woman, as a rule, adapts to this condition. Acute polyhydramnios is extremely rare, develops quickly, complaints are more pronounced, is sometimes observed with monozygotic twins and much more often - with infectious diseases (especially viral) and fetal malformations, usually at 16-24 weeks.

Comparative characteristics of acute and chronic polyhydramnios

Acute polyhydramnios	Chronic polyhydramnios
Occurs very rarely	Occurs frequently
Rapid accumulation of fluid	Fluid accumulation occurs gradually
Detectable up to 20 weeks	It is detected at later stages of gestation.
Fetal abnormalities are detected in 100% of cases	Fetal malformations are not always detected

On the mother's side, polyhydramnios may cause complaints of moderate enlargement of the uterus, increased fetal motor activity, difficulty breathing, abdominal discomfort, pain (in acute polyhydramnios). In the later stages, polyhydramnios may cause signs of threatened miscarriage and premature birth.

The height of the fundus and the abdominal circumference significantly exceed those for the expected gestational age. The uterus is tense, of a hard-elastic consistency, and fluctuations are detected upon palpation. Parts of the fetus are difficult to palpate, the fetus easily changes its position upon palpation, the presenting part is located high above the entrance to the small pelvis, the fetal heart sounds are muffled and poorly audible. Excessive fetal motor activity may be observed. During labor, a tense fetal bladder is detected during vaginal examination, regardless of contractions.

Consequences

Possible complications of pregnancy:

• vomiting (in 36% of pregnant women);
• threat of miscarriage and premature birth;
• late spontaneous abortion, premature birth (7.3%);
• abnormal fetal position (6.5%);
• fetal distress;
• intrauterine growth retardation syndrome;
• late gestosis (5-20%);
• premature rupture of membranes.

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Diagnosis of polyhydramnios

In addition to carefully studying the complaints of the pregnant woman and conducting an external obstetric examination to identify polyhydramnios, performing an ultrasound is of great importance.

Currently, there are 2 main methods for measuring the amount of amniotic fluid using ultrasound:

• Determination of the amniotic fluid index (AFI) is the "gold standard". To determine the AFI, the uterine cavity must be divided into four quadrants. Then, in each quadrant, the depth of the largest pocket of amniotic fluid free of fetal parts is determined. The sum of the four values is the AFI. The diagnosis of oligohydramnios is celebrated in cases where the AFI is below 5%. Polyhydramnios is characterized by an increase in the AFI values of more than 97.5%.

• determination of the size of the largest pocket of fluid free of small parts of the fetus and umbilical cord loops, which is measured in two mutually perpendicular planes. In this case, 2-8 cm is the norm, 1-2 cm is a borderline condition; <1 cm is oligohydramnios: >8 cm is polyhydramnios. Ultrasound helps to diagnose fetal developmental defects that are often encountered with this pathology of the amniotic fluid.

An additional method of examination for polyhydramnios is the triple test (determination of the concentration of α-fetoprotein, human chorionic gonadotropin, and free estriol in the blood serum of a pregnant woman at 16-18 weeks), which makes it possible to suspect fetal malformations and placental pathology. A decrease in prolactin levels compared to the norm for a given gestational age is also a diagnostic sign of polyhydramnios.

Considering the possibility of infectious genesis of polyhydramnios, as well as the important role of iso-serological incompatibility of the blood of the mother and fetus in the development of polyhydramnios, it is recommended to conduct a study for TORCH infection and for antibodies to the Rh factor and hemolysins in ABO or Rh conflict.

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Treatment of polyhydramnios

Pregnant women diagnosed with polyhydramnios are subject to hospitalization and thorough examination to identify the cause of its occurrence (presence of chronic infection, fetal malformations, diabetes mellitus, Rh factor isosensitization, etc.). Treatment of polyhydramnios depends on the nature of the identified pathology. In the presence of fetal malformations incompatible with life, the pregnancy is terminated.

In parallel with pathogenetically justified therapy for acute polyhydramnios, antibiotic treatment (rovamycin, etc.) is performed, and sometimes amniocentesis is performed with the removal of part of the amniotic fluid (the effectiveness of such an intervention is quite low, and the likelihood of complications is high). It should be remembered that amniocentesis is not a therapeutic procedure. After its implementation, the volume of amniotic fluid is quickly restored. There is data on the treatment of polyhydramnios with indomethacin (25 mg every 6 hours), although this may carry a potential risk of premature closure of the arterial duct in the fetus.

The course and management of labor with polyhydramnios

Possible complications of childbirth with polyhydramnios:

• malposition;
• premature rupture of membranes;
• prolapse of umbilical cord loops and small parts of the fetus during the rupture of amniotic fluid;
• weakness of labor (due to overstretching of the uterus, decreased contractile activity);
• premature detachment of the placenta (due to rapid rupture of amniotic fluid);
• bleeding in the afterbirth and early postpartum periods (uterine hypotension due to overstretching).

Therefore, during childbirth it is necessary to carry out prevention of the complications described above.

Particular attention should be paid to the condition of the fetus, given the fact that the level of perinatal losses with polyhydramnios is 2 times higher. Newborns also require special attention, given the possibility of intrauterine infection, congenital malformations, and hemolytic disease.