When a woman is pregnant, the embryo develops inside the amniotic sac, a membrane full of amniotic fluid, which surrounds the baby and plays an important part in its development. Polyhydramnios occurs when there is too much amniotic fluid in the amniotic sac. This causes the uterus to grow excessively and can negatively affect fetal development. Polyhydramnios can occur as early as 16 weeks, though it is most common much later in the pregnancy. The rare condition affects one to two percent of pregnancies.


1. Role of Amniotic Fluid

To understand polyhydramnios, it helps know a little about how a normal pregnancy develops. The amniotic sac forms about 12 days after conception. At this point, the amniotic fluid cushions and protects the embryo and helps maintain temperature. As the fetus develops, it breathes in the fluid to develop the lungs and swallows the fluid as the gastrointestinal system develops. Amniotic fluid also allows the baby to kick and move to aid muscle and bone development and prevents the umbilical cord from being squeezed.

Pregnancy Development Fetus g-stockstudio / Getty Images

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