What are the causes of excessive amniotic fluid?

Many factors can cause polyhydramnios, so expectant mothers also need to pay attention to this. Common neurological malformations, multiple malformations, multiple pregnancies, or pregnant women suffering from gestational diabetes may all cause polyhydramnios.

1. Nervous system malformations:

The most common ones, such as anencephaly and meningocele, account for about 50% of polyhydramnios deformities. Because the meninges are exposed in the amniotic cavity, a large amount of body fluid seeps out through the cerebrospinal fluid, leading to polyhydramnios; secondly, the brain and spinal cord are directly stimulated by the amniotic fluid, resulting in increased urination; thirdly, fetal vasopressin deficiency is also a factor leading to polyhydramnios.

2. Multiple malformations:

In addition to the above-mentioned fetal malformations, congenital cerebrovascular malformations, cardiovascular malformations, pulmonary cystic adenomas, etc. are all related to polyhydramnios. Multi-system and multi-organ malformations are often accompanied by polyhydramnios, and the mechanism is complex. The mechanisms of many diseases are still unclear.

3. Multiple pregnancy

10% of twin pregnancies are complicated by polyhydramnios. The incidence of monozygotic twins is 4 times higher than that of dizygotic twins. Among monozygotic twins, the incidence is highest in monozygotic monochorionic twins, especially twin-twin transfusion syndrome. The vascular anastomosis rate between monozygotic monochorionic twin placentas is as high as 85% to 100%. Vascular anastomosis can be done in two ways: artery-artery, artery-venous, and vein-venous. The most significant approach is arteriovenous anastomosis.

4. Diseases in pregnant women

The incidence of polyhydramnios in pregnant women with diabetes mellitus is significantly increased, accounting for 10% to 25%.

The incidence of polyhydramnios increases in cases of maternal and fetal blood type incompatibility. Polyhydramnios can be caused by anti-fetal blood cell antibodies produced by pregnant women, fetal hemolytic anemia, edema, increased urine volume, and increased placental volume.