The causes of low amniotic fluid are mainly due to fetal malformations, placental hypoplasia, maternal diseases and other factors. 1. Fetal malformation. Amniotic fluid is mainly composed of fetal urine. Low amniotic fluid during pregnancy is likely to be caused by abnormalities in the fetal urinary system, such as renal tubular insufficiency, ureteral obstruction, etc., which will lead to a decrease in fetal urine, thus resulting in a decrease in amniotic fluid. 2. Decreased placental function. The occurrence of overdue pregnancy leads to aging of the placenta or placental hypoplasia, so that the fetus in the uterine cavity of the fetus hypoxia ischemia, which leads to a decrease in renal blood flow and a decrease in the production of urine, resulting in a decrease in the amount of amniotic fluid. 3. Maternal diseases. Pregnant women suffering from gestational hypertension will affect the blood supply of the placenta to reduce, will also appear amniotic fluid reduction. 4. Other factors. In addition, inflammation, intrauterine infection caused by premature rupture of membranes resulting in amniotic fluid leakage, or taking diuretic drugs, dehydration of pregnant women and other conditions, can also lead to low amniotic fluid. Pregnancy check amniotic fluid is also timely and clear causes given after symptomatic treatment, pay attention to drink more water, soy milk and other supplemental amniotic fluid, if necessary, infusion supplemental amniotic fluid.