Pregnancy

The period during which a woman carries a developing fetus, normally in the uterus. Pregnancy lasts for approximately 266 days, from conception until the baby is born, or 280 days from the first day of the last menstrual period. During pregnancy menstruation is absent, there may be a great increase in appetite, and the breasts increase in size; the woman may also experience morning sickness. These and other changes brought about by a hormone (progesterone) produced at first by the ovary and later by the placenta. Definite evidence of pregnancy is provided by various pregnancy tests, by the detection of the heartbeat of the fetus, and by ultrasound.