Why does polyhydramnios affect fetal malformations?

Polyhydramnios is not the main cause of fetal malformations, but fetal malformations may cause polyhydramnios, so pregnant women need to conduct B ultrasound examination in time. If the amniotic fluid index is greater than or equal to 25, it can be judged as polyhydramnios, and fetal malformations should be investigated in time.