Амнион суының жетіспеушілігі және оның салдары

Deficiency of amniotic fluid in the amniotic sac

Oligohydramnios is a medical condition in pregnancy characterized by a deficiency of amniotic fluid, the fluid that surrounds the fetus in the abdomen, in the amniotic sac. It is typically diagnosed by ultrasound when the amniotic fluid index (AFI) measures less than 5 cm or when the single deepest pocket (SDP) of amniotic fluid measures less than 2 cm. Amniotic fluid is necessary to allow for normal fetal movement, lung development, and cushioning from uterine compression. Low amniotic fluid can be attributed to a maternal, fetal, placental or idiopathic cause and can result in poor fetal outcomes including death. The prognosis of the fetus is dependent on the etiology, gestational age at diagnosis, and the severity of the oligohydramnios. The opposite of oligohydramnios is polyhydramnios, or an excess of amniotic fluid.

The amount of amniotic fluid available is based on how much fluid is produced and how much is removed from the amniotic sac. In the first trimester, the main sources of amniotic fluid are fetal lung secretions, transportation of maternal plasma across the fetal membranes, and the surface of the placenta. By the second trimester, the fetal kidneys start to produce urine which becomes the main source of the amniotic fluid for the remainder of the pregnancy. The development of oligohydramnios may be idiopathic or have a maternal, fetal, or placental cause.

The volume of amniotic fluid typically increases until 36 weeks and starts decreasing after 40 weeks in post term gestations. One to two liters of oral hydration can temporarily increase amniotic fluid in dehydrated patients with isolated oligohydramnios. Other investigational therapies may also be useful such as desmopressin, tissue sealants, or sildenafil citrate. These methods are less commonly used and are experimental.

Patients who are preterm are managed in the outpatient setting with weekly or biweekly testing to monitor for accurate fetal growth and decrease chances of unexpected fetal death. This includes a weekly non stress test (NST) and single deepest pocket (SDP) assessment which is also referred to as the modified BPP. The use of oligohydramnios as a predictor of gestational complications is controversial. Potter syndrome is a condition caused by oligohydramnios. Affected fetuses develop pulmonary hypoplasia, limb deformities, and characteristic facies. Bilateral agenesis of the fetal kidneys is the most common cause due to the lack of fetal urine.