Effect of double embryo transfer derived from autologous frozen oocytes on multiple pregnancy rates and presentation of success rates stratified by age at retrieval

OBJECTIVE: To compare outcomes transferring one or two embryos in autologous frozen oocyte cycles. MATERIAL AND METHODS: A retrospective cohort study conducted at an academic fertility center between January 2012 and December 2018. One-hundred and fourteen patients underwent frozen oocyte transfers; 67 single embryo transfer (SET) and 47 double embryo transfer (DET). No subjects had more than two embryos transferred. Data were analyzed using t-test and chi-squared testing. Multivariate logistic regression was used to control for confounding effects. Power analysis suggested an 82% power with alpha of 5% and effect size of 27%. RESULTS: Regarding the embryo stage, 72% were cleavage embryos and 28% were blastocyst embryos. Among those who had cleavage stage embryos, 48.8% underwent SET and 51.2% underwent DET. In the blastocyst embryos group these proportions were 84.4% and 15.6%, respectively. There were no difference in pregnancy rate for SET (40.3%) vs DET (36.2%) (p=0.78). Additionally, the live birth rate did not differ between SET and DET (28.4 vs 19.1%, respectively, p=0.26). The multivariate multilevel analysis provided adjusted odds ratios (95% confidence interval) of: 1.85 (0.46-7.44) for pregnancy; 0.497 (0.05-4.86) for clinical pregnancy; and 0.82 (0.11-6.29) for live birth when comparing SET and DET. Multiple pregnancy rates were significantly lower in the SET (0%), compared with DET group (44.4%) (p<0.002). CONCLUSION: SET results in excellent live birth outcomes in autologous frozen oocyte cycles. However DET results in significantly increased rates of multiple pregnancies. This suggests that SET is a viable option in autologous frozen oocyte cycles.