Obstetrician-gynecologist - A physician specializing in the health care of women, including pregnant women, and the delivery of babies.

Ovaries - The two reproductive organs that produce female hormones and release eggs for fertilization.

Ovulation - The release of an egg from the ovaries, normally occurring every month.

Oxytocin - This hormone secreted by the pituitary gland triggers labor contractions and the let-down reflex in nursing mothers. Pitocin is a synthetic form of the hormone.