The causes of excessive amniotic fluid are fetal factors, placental factors, maternal diseases and other factors. 1. Fetal factors: The fetus itself suffers from certain diseases in the mother’s body, such as neural tube malformation, cerebrospinal fluid extravasation, which leads to excessive amniotic fluid. In addition, if the fetus has atresia of the esophagus or duodenum, the fetus can not swallow the amniotic fluid, which can also lead to excessive amniotic fluid. 2. Placental factors: for example, the placenta is relatively large, the umbilical cord is attached abnormally, clinically, the more common is the sail-shaped placenta, the placenta is very large may also lead to excessive amniotic fluid. 3. Diseases of pregnant women: Gestational diabetes mellitus is common in obstetrics, which can also lead to excessive amniotic fluid. 4. Other factors: in the clinical examination after excluding maternal diseases and fetal factors, another 30% can not find any reason, is relatively simple amniotic fluid, in this case, pregnant women do not need to worry too much, only need to listen to the doctor for regular checkups can be. If a pregnant woman has excessive amniotic fluid, it is recommended that she be examined in time to determine the cause of the condition, so as to avoid delaying the condition.