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Amniotic fluid and amniocentesis
Last reviewed: 19.10.2021
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The amniotic fluid is produced by the cells of the amnion and the filtration of the blood plasma of the mother, the volume of this fluid depends on the vital activity of the fetus. At the 10th week of pregnancy, the volume of amniotic fluid is 30 ml, on the 20th - 300 ml, on the 30th - 600 ml. The maximum volume is reached between the 34th and 38th week (800-1000 ml), and then it begins to decrease by 150 ml per week.
[Indications for amniocentesis
A significant (from obstetrical position) age of the mother (if the mother is older than 35-37 years, the fetus has a higher risk of developing Down's syndrome); the previous child had a defect in the formation of the nervous system (subsequent fruits are affected with a frequency of 1:20), an increase in the level of alpha-fetoprotein in the mother; cases where one of the parents is the carrier of a proportional chromosomal translocation (1 of 4-10 chances for the corresponding pathology of the fetus); risk of inheritance from a recessive type of metabolic disease (currently, 70 metabolic disorders can be recognized); the mother of a carrier associated with an X-chromosome (for early identification of the sex of the fetus). The frequency of miscarriages after amniocentesis is 1-2%.
Amniocentesis
Amniocentesis is a puncture of the amniotic fluid to produce a sample of the amniotic fluid. The procedure is carried out for the purpose of prenatal diagnosis of fetal developmental anomalies, for determining the tactics of conducting a Rh-conflict pregnancy, and also for assessing the degree of maturity of the fetus (for example, its lungs). To diagnose the developmental fetus, amniocentesis is performed at the 16th week of pregnancy, when there is already enough amniotic fluid for the technical implementation of the procedure, but it is not too late to terminate the pregnancy in the event of unfavorable results. Ultrasonic monitoring makes it possible to take the amount of amniotic fluid required for analysis, while avoiding penetration of the placenta. Following the rules of aseptic and antiseptic and using a puncture needle of G21 caliber, 15 ml of the desired liquid are obtained. After this procedure, Rh-negative pregnant intramuscularly injected 250 units. Anti-D-immunoglobulin.
Malododia
The volume of the amniotic fluid is less than 200 ml. It is rare. It can be associated with a delayed pregnancy, a protracted process of rupturing membranes of the amniotic membrane, placental insufficiency, aplasia of the urethra, or agenesis of the kidneys in the fetus. Potter's syndrome (with a fatal prognosis) is manifested by a poor ears location in the fetus, renal agenesis, lung hypoplasia, and nodular amnion (agglutination of fetal skin scales).
Polyhydramnios
It occurs with a frequency of 1: 200 pregnancies. The volume of amniotic fluid exceeds 2-3 liters. In 50% of cases, polyhydramnios are combined with malformations of the fetus, in 20% - with diabetes maternal. In 30% of cases, there are no visible causes for polyhydramnios. Causes of polyhydramnios associated with the fetus: anencephaly (no swallowing reflex), spina bifida (open or skin-covered spina bifida, absence of arches of several vertebrae, mainly in the lumbar region); umbilical hernia; ectopia of the gallbladder, bladder; atresia of the esophagus or duodenum; dropsy of the fetus; excessive extensor posture of the fetus. The causes of polyhydramnios associated with the state of the mother: diabetes mellitus, multiple pregnancies. At the very beginning of the third trimester of pregnancy, polyhydramnios can be manifested by complaints from the mother for shortness of breath and swelling. Circumference of the abdomen of the patient more than 100 cm should suggest the possibility of polyhydramnios. To exclude multiple fetuses and malformations of the fetus, ultrasound is used. Polyhydramnios predispose to premature birth, poor presentation of the fetus, prolapse of the umbilical cord and postnatal bleeding (the overgrown uterus does not shrink due images). During labor during polyhydramnios, it is necessary to plan in advance measures to control the possible prolapse of the umbilical cord. After childbirth, the neonatal nasogastric catheter should be inserted to check the passage of the esophagus (to exclude its atresia).