In vitro fertilization: past and future.

The current clinical status of in vitro fertilization is reviewed including ovarian stimulation, fertilization, implantation after replacement and luteal phase support. The evolution of singleton or multiple pregnancies after IVF is discussed; pregnancy loss can occur after ectopic pregnancy or abortion. Several new scientific advances are described: the cryopreservation of embryos, the studies on the metabolism of embryos by non-invasive methods and the use of fetal tissues to restore abnormal conditions in adults. The current ethical issues of IVF are discussed: freezing of embryos, oocyte and embryo donation, surrogate motherhood as well as the rights of an early embryo and the ethics of embryo research.