Pregnancy, in humans, is the nine-month period from the fertilization and implantation of an ovum (egg), the development of embryo and fetus through the birth of a child. Interruption of menstruation and change in structure and shape of the mammary glands (breasts) are early signs; morning sickness, which may be mild or incapacitating, is a common symptom. Later an increase in abdominal size is seen and other abdominal organs are pushed up by the enlarging uterus (womb). Ligaments and joints become more flexible in preparation for delivery. Multiple pregnancy, hydatidiform mole, spontaneous abortion, antepartum hemorrhage, toxemia, and premature labor are common disorders of pregnancy. The time following birth is called puerperium.