A womb is also called a uterus. It is a sac shaped organ in the lower abdomen area which houses the baby during pregnancy. It expands as the baby grows inside it. When an egg is released from the ovaries (called ovulation) the womb prepares a blood lining so that if the egg is fertilized by male sperm it can be nourished by the blood lining. If the egg is not fertilised this lining is not needed so it is sent out of the body as a menstrual period.
Attribution: Straight Talk Foundation & Marie Stopes