Premature discharge of amniotic fluid

Premature rupture of membranes is their spontaneous rupture before the onset of labor in pregnancy periods from 22 to 42 weeks. The incidence of premature rupture of membranes is from 10 to 15% depending on the gestational age.

Amniotic fluid is a biologically active environment surrounding the fetus, intermediate between it and the mother's body, which performs various functions throughout pregnancy and labor. Normally, their amount is about 600 ml; fluctuations depend on the gestational age - from 300 ml (at 20 weeks) to 1500 ml (at 40 weeks). In full-term pregnancy, amniotic fluid is a product of secretion of the amniotic epithelium, transudation from the vessels of the decidual membrane and the function of the fetal kidneys, excreted by the placental and paraplacental pathways. In 1 hour, 200-300 ml of amniotic fluid is replaced, and complete - within 3-5 hours. In addition, amniotic fluid is the most important part of the defense system, preventing mechanical, chemical and infectious effects. In physiological pregnancy, amniotic fluid remains sterile. Amniotic fluid has antimicrobial activity due to the production of interferon by the fetal membranes, contains lysozyme, antibodies to some types of bacteria and viruses, and immunoglobulins.

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Causes of Premature Rupture of Membranes

There are several causes for the etiology of premature rupture of membranes:

• infection (amnionitis, ervicitis, vaginitis of streptococcal or other etiology);
• overstretching of the uterus (polyhydramnios and/or multiple pregnancy);
• narrow pelvis;
• extension insertion of the head;
• breech presentation;
• malposition;
• fetal malformations;
• structural changes in tissues (due to insufficient consumption of ascorbic acid and microelements, in particular copper);
• injury.

The most common factor is infectious. Ascending cervical and vaginal infection leads to seeding with bacteria that secrete collagenase, which reduces the strength and elasticity of the fetal membranes.

A direct link has been established between the intake of vitamin C and the degree of collagen degradation leading to premature rupture of membranes. A link has been found with the level of insulin-like factor in vaginal secretions, with an increase in which the risk of premature rupture of membranes increases sharply. Based on this, the role of ascorbic acid, a-tocopherol, retinol and beta-carotene in the prevention of premature rupture of membranes has been confirmed. In addition, it has been proven that the mechanical strength of the fetal bladder depends on the content of surface-active phospholipid (amniotic surfactant).

With the onset of labor, the bactericidal activity of amniotic fluid decreases; it can delay the development of microorganisms for only 3-12 hours, and subsequently becomes a breeding ground for their reproduction.

With the rupture of the fetal membranes, the possibility of microorganisms penetrating into the amniotic fluid increases significantly until the moment of delivery. If the anhydrous period lasts over 6 hours, 50% of children are born infected; if it lasts over 18 hours, the contamination of the amniotic fluid increases sharply. The development of chorioamnionitis and postpartum infectious complications is observed in 10-15% of cases, despite the preventive measures taken.

The most common complication of labor with premature rupture of membranes is weakness of labor. Primary weakness of labor is observed 5.7 times more often, and secondary weakness is 4 times more often compared to physiological labor. This is explained by the lack of increase in prostaglandin concentration after premature rupture of membranes, inhibition of lipid peroxidation processes, insufficient oxytocin, low production of prostaglandin by chorionic cells due to high production of progesterone.

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Diagnosis of premature rupture of membranes

When examining the cervix in mirrors, amniotic fluid is visually detected flowing from the cervical canal. In case of difficulties in establishing a diagnosis, amniotic fluid and urine, increased secretion of amniotic fluid and cervical glands before childbirth are differentially examined using one or more of the following tests:

• nitrazine. A few drops of fluid taken from the vagina are applied to a strip of nitrazine paper. If amniotic fluid is present, the paper turns dark blue;
• fern test - a phenomenon of formation of a fern leaf pattern (arborization). A cotton swab is used to collect material from the external os of the cervical canal, a thin layer is applied to a clean glass slide, after which the preparation is dried in air for 5-7 minutes. The preparation is examined under a microscope at low magnification. Determination of crystallization in the form of a fern leaf or a tree-like structure confirms the presence of amniotic fluid. The "fern leaf" that is formed during arborization of amniotic fluid has more branches than during arborization of cervical mucus. The fern test is considered more accurate than the nitrazine test;
• cytological. The detection of amniotic fluid cells in a vaginal smear gives fewer false results than the nitrazine test and may be the most accurate for confirming the diagnosis;
• pH determination using a test strip. Amniotic fluid has an alkaline reaction (pH 7.0-7.5), and vaginal contents are normally acidic (pH 4.0-4.4). A sterile cotton swab is used to collect material from the external os of the cervix and apply it to a test strip. If the strip turns blue-green (pH 6.5) or blue (pH 7.0), this indicates the presence of amniotic fluid in the material being tested. False positive results are possible if blood, urine, or antiseptics get into the material being tested;
• examination of vaginal smears using the method of L. S. Zeyvang. 1-2 drops of vaginal contents are applied to a glass slide and 1-2 drops of a 1% aqueous solution of eosin are added, followed by viewing in a light-optical microscope at low magnification. In the case of amniotic fluid leakage, clusters of unstained anuclear cells of the fetal epidermis are determined among the bright pink epithelial cells of the vaginal contents and erythrocytes in the fluid being examined, which do not accept the dye due to being coated with vernix caseosa;
• ultrasound. If a sufficient amount of amniotic fluid is detected, the diagnosis of premature rupture of membranes is questionable. In case of oligohydramnios detection and at least one positive test for amniotic fluid, the diagnosis of premature rupture of membranes is established.

Spontaneous labor (without attempts to induce it) during full-term pregnancy develops in 70% of pregnant women during the first 24 hours from the moment of detection of rupture of the membranes, and in 90% - in the first 48 hours. Expectant tactics in these cases, in the absence of clinical manifestations of infection and timely antibiotic prophylaxis, does not increase the frequency of purulent-inflammatory complications in the mother and the newborn.

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Management of pregnant women with premature rupture of membranes

Hospitalization in a level III obstetric hospital is required from the 22nd to the 34th week of pregnancy. Before transferring a pregnant woman from level I-II obstetric hospitals to level III institutions, an external obstetric examination, examination of the cervix in mirrors and auscultation of the fetal heartbeat are performed. If premature rupture of membranes is confirmed, it is necessary to begin prevention of respiratory distress syndrome: dexamethasone is administered intramuscularly at 6 mg every 12 hours, for a course of 24 mg (A) or betamethasone at 12 mg every 24 hours, for a course of 24 mg (A).

From the 35th week of pregnancy, childbirth can be carried out in level II healthcare institutions, if necessary, by calling a consultant from a healthcare institution providing higher level healthcare.

The main stages of examination in a hospital during hospitalization:

• establishment of gestational age;
• determination of the approximate time of rupture of membranes based on anamnesis data;
• diagnostics of the presence of labor using external examination methods;
• examination of the cervix using speculums (vaginal examination is not performed in the absence of labor and contraindications to expectant management of the pregnant woman);
• confirmation of diagnosis by laboratory methods in doubtful cases;
• Ultrasound with determination of the volume of amniotic fluid;
• bacterioscopic examination of vaginal discharge with Gram staining of smears.

Management of pregnant women with premature rupture of membranes

Depending on the gestational age, concomitant pathology, obstetric situation and obstetric-gynecological history, an individual management tactic is selected.

In all cases, the patient and her family must receive detailed information about the condition of the pregnant woman and the fetus, the benefits and possible risks of one or another method of further pregnancy management, and obtain the patient’s written consent.

Expectant management (without induction of labor) can be chosen:

• in pregnant women with a low degree of predicted perinatal and obstetric risk;
• if the condition of the fetus is satisfactory;
• in the absence of clinical and laboratory signs of chorioamnionitis (an increase in body temperature above 38 °C, a specific odor of amniotic fluid, fetal heart rate over 170 beats per 1 min; the presence of two or more symptoms provides grounds for establishing a diagnosis of chorioamnionitis);
• in the absence of complications after the rupture of amniotic fluid (prolapse of the umbilical cord, placental abruption and the presence of other indications for urgent delivery).

If a wait-and-see approach is chosen, the following must be carried out in the obstetric hospital:

• measuring the body temperature of a pregnant woman twice a day;
• determination of the number of leukocytes in peripheral blood depending on the clinical course, but not less than once a day;
• bacterioscopic examination of vaginal discharge once every three days (with counting the number of leukocytes in the smear);
• monitoring the condition of the fetus by auscultation twice a day and, if necessary, recording CTG at least once a day from the 32nd week of pregnancy;
• warn the pregnant woman about the need to independently conduct a fetal movement test and contact the doctor on duty in the event of a change in fetal motor activity (too slow or too vigorous);
• prophylactic administration of semi-synthetic penicillins or second-generation cephalosporins in average therapeutic doses from the moment of hospitalization for 5-7 days in the absence of signs of infection in the pregnant woman.

At 22-25 weeks of pregnancy:

• monitoring of the condition of the pregnant woman and the fetus without conducting an internal obstetric examination is carried out in the conditions of an obstetric hospital of the third level of medical care;
• Antibacterial therapy from the moment of hospitalization in the obstetric hospital.

At 26-34 weeks of pregnancy:

• monitoring of the condition of the pregnant woman and the fetus without conducting an internal obstetric examination is carried out in the conditions of an obstetric hospital of the third level of medical care;
• antibacterial therapy from the moment of hospitalization in the obstetric hospital;
• prevention of fetal respiratory distress syndrome by intramuscular administration of dexamethasone at 6 mg every 12 hours (for a course of 24 mg) or betamethasone at 12 mg every 24 hours (for a course of 24 mg). Repeated courses of prevention are not carried out.

At 35-36 weeks of pregnancy:

• wait-and-see or active tactics are possible;
• if the condition of the pregnant woman and the fetus is satisfactory and there are no indications for operative delivery, observation is carried out without an internal obstetric examination in healthcare institutions of the II-III level of medical care;
• Antibacterial therapy begins after 18 hours of the anhydrous period;
• if spontaneous labor does not develop within 24 hours, an internal obstetric examination is performed;
• with a mature cervix, induction of labor begins in the morning (not earlier than 6:00) with oxytocin or irostaglandins;
• in case of an immature cervix, preparation for childbirth is carried out by intravaginal administration of prostaglandin E2;
• If indicated, delivery is performed by cesarean section.

At 37-42 weeks of pregnancy:

• if spontaneous labor does not develop within 24 hours, an internal obstetric examination is performed;
• with a mature cervix, labor is induced in the morning (not earlier than 6:00) with oxytopane or prostaglandin E2;
• in case of an immature cervix, preparation for childbirth is carried out by intravaginal administration of prostaglandin E2;
• If there are indications, delivery is performed by caesarean section.

Tactics of managing pregnant women with infectious complications

In case of development of chorioamnionitis, termination of pregnancy is indicated.

In the treatment regimen, cephalosporins of the II-III generation and metronidazole (or ornidazole) are prescribed 30 minutes before the administration of cephalosporins.

The method of delivery is determined by the gestational age, the condition of the pregnant woman and the fetus, and the obstetric situation.

In case of operative delivery, intensive antibacterial therapy is administered in a therapeutic regimen for at least 7 days.

Thus, premature rupture of membranes is accompanied by a number of serious complications, which requires improvement of the tactics of labor management and antenatal protection of the fetus in this pathology, prevention of purulent-inflammatory diseases in the mother and the newborn, as well as special attention in the management of the early neonatal period.

ICD-10 code

According to the International Classification of Diseases, 10th revision (ICD-10), the code for premature rupture of membranes is 042:

• 042.0 Premature rupture of membranes within 24 hours before onset of labor;
• 042 1 Premature rupture of membranes, onset of labor after 24 hours of anhydrous period;
• 042.2 Premature rupture of membranes, delayed labor associated with therapy;
• 042.9 Premature rupture of membranes, unspecified.