What is the reason for excessive amniotic fluid in late pregnancy?

The importance of amniotic fluid to the fetus is well known. However, the situation of each pregnant woman is different, and the amount of amniotic fluid is also different. If there is too little amniotic fluid in the late pregnancy, it is easy to cause malnutrition or hypoxia and suffocation of the fetus. On the contrary, the hidden dangers of too much amniotic fluid cannot be ignored. So what is the reason for more amniotic fluid in the late pregnancy?

1. Fetal malformation Among pregnant women with polyhydramnios, about 20% to 50% have fetal malformations, among which central nervous system and upper gastrointestinal tract malformations are the most common. In fetuses with anencephaly, encephalocele and spina bifida, the meninges are exposed, the choroidal tissue proliferates, and the exudate increases, leading to polyhydramnios. Infants with anencephaly and severe hydrocephalus lack central swallowing function, swallowing reflex and antidiuretic hormone, which leads to increased urine volume and polyhydramnios. In cases of esophageal or small intestinal atresia and pulmonary hypoplasia, the inability to swallow and inhale amniotic fluid can lead to polyhydramnios due to accumulation of amniotic fluid.

2. Multiple pregnancy The incidence of polyhydramnios in multiple pregnancy is 10 times that of single pregnancy, especially in monozygotic twins, and often occurs in one of the fetuses with a larger weight. This is because the blood circulation between the monozygotic twins is mutually communicated, and the dominant fetus has more circulating blood and increased urine volume, resulting in polyhydramnios.

3. Various diseases of pregnant women and fetuses such as diabetes, ABO or Rh blood type incompatibility, severe fetal edema, pregnancy-induced hypertension, acute hepatitis, and severe anemia in pregnant women. The blood sugar level of the fetus of a diabetic pregnant woman will also increase, causing polyuria and being discharged into the amniotic fluid. When the blood types of mother and fetus are incompatible, the placenta is heavier. It has been reported that when the placenta weight exceeds 800g, 40% of them are combined with polyhydramnios, and the pathological basis is chorionic edema affecting fluid exchange.

4. Placental and umbilical cord lesions Placental chorioangioma and umbilical cord velamentous adhesion can sometimes cause polyhydramnios.

5. Idiopathic polyhydramnios accounts for about 30%, without any abnormalities of the pregnant woman, fetus or placenta, and its cause is unknown.

From the above introduction, everyone is very clear about the reasons for excessive amniotic fluid in the late pregnancy. If the phenomenon of excessive amniotic fluid occurs, you must consult a doctor. Of course, during the prenatal check-up, if the problem of excessive amniotic fluid is found, the doctors will take corresponding measures to deal with it according to the specific situation of the pregnant woman and the fetus.