Causes of oligohydramnios: fetal anomalies, term pregnancy, IUGR, decreased uteroplacental blood flow, amniotic membrane pathology. Hyponatremia occurs before 28 weeks of gestation and should be examined in detail for fetal malformations. After the detection of oligohydramnios in late pregnancy and the exclusion of fetal malformations, good prenatal care should be provided for the early detection and prevention of pregnancy complications and complications, such as hyperemesis gravidarum, IUGR, and so on. For those who need to continue pregnancy without obvious fetal abnormalities, regular ultrasound examination should be performed to determine the amount of amniotic fluid, and fetal heart electronic monitoring should be performed to understand the function of the placenta. If the pregnancy is complicated by hyponatremia, the pregnancy should be terminated as soon as the diagnosis is confirmed. If the fetus is abnormal or contaminated with meconium, cesarean section should be performed to avoid perinatal complications.