Embryo cryopreservation at the pronuclear stage and efficient embryo use optimizes the chance for a liveborn infant from a single oocyte retrieval

Objective: To estimate the potential for a liveborn in our program achieved through either fresh or frozen embryos derived from a single oocyte retrieval. Design: Retrospective analysis. Setting: A tertiary referral reproductive medicine unit. Patient(s): All consecutive patients undergoing oocyte retrieval from January 1, 1996, to June 30, 1997. Intervention(s): All couples undergoing IVF-ET at our center are counseled about a specific embryo transfer number after oocyte retrieval based on demographic and historical factors. Only this specified number of embryos is retained in culture. All normally fertilized (2PN) oocytes exceeding this number are immediately cryopreserved at the pronuclear stage. For couples who do not conceive after fresh embryo transfers, frozen embryo transfers are subsequently performed by usually thawing only the number of embryos intended for transfer, thereby conserving remaining embryos for further potential frozen embryo cycles. Main Outcome Measure(s): Liveborn delivery per oocyte retrieval. Result(s): From January 1, 1996 to June 30, 1997, 261 oocyte retrievals were performed, resulting in 245 fresh transfers. Embryos were cryopreserved after 75.9% of retrievals. Through June 30, 1998, 103 frozen transfers were performed (excluding frozen transfers occurring after a liveborn delivery). Rates of liveborn deliveries occurring from oocytes derived from a single retrieval for patients aged <35.0 years, 35.0-39.0 years, and >39.0 years were 61.2%, 59.7%, and 18.5%, respectively. Conclusion(s): For women <39 years of age, the efficient use of embryo cryopreservation at the pronuclear stage and economical embryo utilization policies results in cumulative chances for a liveborn exceeding 60%. (C)2000 by American Society for Reproductive Medicine.