In vitro fertilization (IVF): Refers to fertilization taking place outside the body in a laboratory Petri dish. There, the egg of a female partner or donor is joined with sperm. With IVF, the ovaries must be overly stimulated, usually with fertility drugs that allow retrieval of multiple mature eggs. After 48 to 72 hours of incubation, the fertilized egg (embryo) is inserted in the uterus and normal pregnancy should result. While IVF is employed mostly for women with obstructed fallopian tubes, it is occasionally used for men with low (oligospermia) or absence (azoospermia) sperm production.