In vitro fertilization (IVF) is a fertility treatment in which eggs and sperm are paired outside the body in a laboratory. It's a strategy used by people who need help getting pregnant. IVF is a successful assisted reproductive technology that involves several complex phases. The fertilized egg, now referred to as an embryo, is implanted into a uterus a few days following fertilization. Pregnancy occurs when this embryo places itself into the wall of the uterus.