Optimization of culture conditions for human in vitro fertilization and embryo transfer.

Approximately 20 years ago the first child conceived with in vitro fertilization (IVF) and embryo transfer was born in England. Although overall pregnancy rates and delivery rates after IVF have improved over the years, success between IVF clinics can vary as much as tenfold. The factors that influence the success rate include type of patient, ovarian stimulation protocol, quality of oocytes, culture conditions, handling of gametes and embryos, quality of embryos, embryo transfer technique, and endometrial receptivity. Culture conditions and handling of gametes and embryos will be reviewed with the hope of improving success of human IVF. The ongoing clinical pregnancy rates in our program increased from about 30% in 1995 and 1996 to about 50% in 1997. Improved embryo culture conditions and embryo cryopreservation technology should not only increase fresh but also frozen-thawed embryo transfer pregnancy. This will make IVF efficient and cost-effective while achieving high overall pregnancy rates with lower multiple pregnancy rates.