Multiple gestations in assisted reproductive technology: Can they be avoided with blastocyst transfers?

OBJECTIVE: Blastocysts are advanced-stage embryos with high implantation po tential; theoretically, limited numbers of blastocysts can be used for embr yo transfer to achieve good pregnancy rates with low multiple pregnancy rat es. Clinical outcomes of a newly implemented blastocyst transfer program we re evaluated. STUDY DESIGN: This study is a retrospective analysis of 553 blastocyst tran sfer cycles performed by a university-based in vitro fertilization program; risk factors associated with multiple gestations were analyzed. RESULTS: An average of 2.2 embryos were used for embryo transfer. The overa ll clinical pregnancy rate per embryo transfer was 45.1%; multiple gestatio n, twin, and triplet rates were 40.9%, 36.5%, and 4.3%, respectively. Multi ple gestations increased significantly (1) when embryo transfer was done on day 5, (2) when greater than or equal to2 blastocysts were present on day 5, and (3) when maternal age was less than or equal to 30 years. CONCLUSION: In spite of a conservative approach to the number of blastocyst s used for embryo transfer, the overall multiple pregnancy rate was high, a nd triplet pregnancies did occur.