A PROSPECTIVE, RANDOMIZED STUDY OF EMBRYO-TRANSFER RESULTS AFTER 3 OR5 DAYS OF EMBRYO CULTURE IN IN-VITRO FERTILIZATION

Objectives: To compare the implantation rate of embryos after 3 and 5 days of IVF culture. Design: Prospective randomization of ET depending on the weekday of ovum pick-up (OPU). Setting: University Department of Endocrinology and Reproduction. Patients: All women entering an out clinic IVF program. Interventions: Two hundred thirty-three ETs perfor med on day 3 after OPU and 410 performed on day 5 were analyzed. When blastocysts with a clear inner cell mass were available, a maximum of two were replaced. Results: On day 3 after OPU, 60 pregnancies per 233 ET (26%) and on day 5, 102 pregnancies per 410 ET (25%) were induced. The average implantation rate per embryo was 13% and 12%, respectivel y. After subdivision according to embryo morphology, pregnancy rate pe r ET (n = 59) and implantation rate per embryo on day 3 with exclusive ly unfragmented embryos were 32% and 18%, respectively, not significan tly different from ET (n = 73) exclusively with embryos containing >0% and <20% fragments: 27% and 12%. After transfer on day 5, when one or more cavitating embryos were available (n = 227), pregnancy and impla ntation rates were 40% and 23%, statistically different from ET on day 3. On day 5, ET exclusively with morula stages showing signs of start ing blastulation (n = 26), pregnancy rate and implantation rate were 1 2% and 11%, respectively, from ET (n = 157) with embryos not reaching the latter stage: 6% and 3%. Conclusions: Overall ET results after 3 a nd 5 days are comparable. After 5 days of culture, one to two embryos can be replaced with an average implantation rate of >23% per embryo, minimizing the incidence of triplets.