P02: Fetus and newborn affected by complications of placenta, cord and membranes

P02.3: Fetus and newborn affected by placental transfusion syndromes

The placenta forms in the mother’s womb during pregnancy. The placenta consists of cells from the mother and cells from the unborn child. The umbilical cord connects the child to the placenta. During pregnancy the umbilical cord connects the child's blood circulation to the mother's. The child receives nutrients and oxygen via the blood vessels in the umbilical cord. When the pregnancy begins, the amniotic sac containing the amniotic fluid develops in the womb. The amniotic sac surrounds the child.

An exchange of blood can occur when the pregnancy involves twins, for example. If the twins share a placenta, their blood circulation systems are connected to one another via the placenta. As a result, blood flows from one twin to the other. If the twins have separate amniotic sacs, there can be differing amounts of amniotic fluid in the sacs as a result of the blood exchange. If blood flows from one twin to the other, the twins may also be different sizes. One of the twins may receive less oxygen and nutrients so that it grows less. Defects can also occur in one or both twins.

A blood exchange can also occur between mother and child. Nutrients and oxygen are exchanged via the placenta. When blood is exchanged between the mother and child, the child's blood can get into the mother's circulatory system. Then the child may lose blood. As a result, the child gets a poorer supply of oxygen. The child may then move less than before in the womb.