P50: Fetal blood loss

P50.4: Haemorrhage into maternal circulation

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.

In most pregnancies, small amounts of infant blood get into the mother's circulatory system via the placenta. If the placenta gets injured, however, larger amounts of infant blood may get into the mother's circulatory system. Operations on the womb during pregnancy can also cause blood to get transferred. If the placenta detaches from the womb before the birth, infant blood can also get into the mother's circulatory system.

If a large amount of blood is transferred to the mother's circulatory system, it means blood is lost. This can be life-threatening. The child may then be inadequately supplied with oxygen. The heart may also beat more slowly than usual. The child may then move about less than usual in the womb.