What problems occur to a fetus who swallows amniotic fluid?

The swallowing and subsequent inspiration and aspiration of amniotic fluid is a normal process that occurs throughout fetal life. In fact, the amniotic fluid volume and swallowing increase markedly during the last few weeks of pregnancy, indicating the importance of this process for fetal lung development.

In contrast, an impaired ability of the fetus to swallow and properly coordinate this process with respiration causes a rare but serious condition known as polyhydramnios, in which excessive amniotic fluid accumulates. Polyhydramnios can cause maternal complications and increased risk of fetal malformation, pulmonary hypoplasia (underdevelopment of the lungs), hydrops (excessive fluid collection within fetal tissues and body cavities), and fetal demise.

In addition, polyhydramnios resulting from impaired fetal swallowing, as may be the case in neuromuscular diseases, causes oligohydramnios (low amniotic fluid volume) to occur postnatally due to the impaired ability to swallow and produce saliva.