Implantation rates after in vitro fertilization and transfer of a maximum of two embryos that have undergone three to five days of culture.

OBJECTIVE: To evaluate implantation and pregnancy rates in patients undergoing IVF after the transfer of a maximum of two embryos that had been cultured for 3-5 days.
DESIGN: Prospective study.
SETTING: An IVF laboratory at a tertiary referral university hospital. PATIENT(S): One thousand seven hundred eighty-seven couples who underwent their first IVF cycle between January 1995 and December 1997. INTERVENTION(S): In vitro fertilization and transfer of embryos after 3, 4, or 5 days of culture using a single medium without coculture. MAIN OUTCOME MEASURE(S): Implantation and pregnancy rates. RESULT(S): Overall implantation and pregnancy rates were not significantly different with different culture periods. Forty-one percent of all available embryos developed into blastocysts on day 5. The transfer of at least one good-quality blastocyst could be performed in 62% of patients. Blastocysts had an implantation rate of 26% per embryo, whereas the implantation rate of eight-cell embryos on day 3 was 18%. Implantation rates for retarded, normal, and advanced embryos were not significantly different with an extended culture period. CONCLUSION(S): Under the study conditions, the transfer of embryos after 5 days rather than 3 days of embryo culture did not change the overall implantation and pregnancy rates. The implantation potential of embryos available for transfer can be assessed better after an extended culture period. Five days of culture allows the transfer of a reduced number of embryos without decreasing overall pregnancy rates.