An (spontaneous) abortion is the loss of a fetus by natural causes before week 20 of pregnancy. However, the loss of a fetus by natural causes after week 20 of pregnancy is called dead fetus.
Before an abortion, the woman usually suffers little bleeding until she has a more evident haemorrhage together with vaginal secretion. The uterus contracts and the woman will feel a pain similar to cramps. If the abortion continues, the haemorrhage, the secretion and the pains increase. In the end, part or even all of the content of the uterus can be expelled. When only a part is expelled (incomplete abortion), an expansion and suction must be done to drain the uterus.