When the ruptured fetal membranes have leaked most of the fluid that keeps the fetus 'floating' in the uterus, the membranes collapse around the baby, and the baby can press against the uterine wall. It can lie on and compress the umbilical cord, so the fetus becomes short of oxygen and the waste product carbon dioxide builds up in its body.

Deficiency of oxygen and accumulation of carbon dioxide in the body is called hypoxia (literally 'low oxygen'), which rapidly leads to asphyxia (brain and tissue damage due to hypoxia) resulting in death if oxygen is not quickly restored.

The fetus can also develop asphyxia and die because of partial or complete placental abruption, as described next.

Last modified: Friday, 11 July 2014, 1:14 PM