Frozen-thawed blastocyst transfer reduces ectopic pregnancy risk: an analysis of single embryo transfer cycles in Japan

Objective: To evaluate the effect of frozen-thawed blastocyst transfer on ectopic pregnancy (EP) rate. Design: Retrospective analysis. Setting: Japanese registry of assisted reproductive medicine. Patient(s): Women who were registered during 2008. Intervention(s): None. Main Outcome Measure(s): Rates of live birth, EP, and spontaneous abortion in single blastocyst and cleavage-stage ET cycles in both fresh and frozen-thawed were determined. Result(s): In the frozen-thawed single blastocyst transfer cycles, 84 EPs of 10,312 clinical pregnancies (0.81%) were reported. There were 25 EPs of 1,361 clinical pregnancies (1.8%) in fresh IVF single blastocyst transfer cycles and 19 of 1,352 (1.4%) in fresh intracytoplasmic sperm injection single blastocyst transfer cycles. The rate of EPs after frozen-thawed single blastocyst transfers varied between 0.56% and 0.97% after stratification by age group. Conclusion(s): Frozen-thawed blastocyst transfers have reduced EP rates significantly compared with fresh blastocyst transfers. (Fertil Steril (R) 2011; 95: 1966-9. (C)2011 by American Society for Reproductive Medicine.)