Comparative study of pregnancy outcomes between day 3 embryo transfer and day 5 blastocyst transfer in patients with progesterone elevation

Objective To explore the effects of progesterone (P) elevation on pregnancy outcomes of day 3 embryo and day 5 blastocyst transfer.Methods Clinical outcomes (pregnancy and ectopic pregnancy rates) following day 3 embryo and day 5 blastocyst transfer cycles were retrospectively analysed. Day 3 embryo and day 5 blastocyst transfer cycles were divided into normal P level (P ≤ 1.5 ng/ml) and P elevation group (P > 1.5 ng/ml), based on the serum P level on the day of human chorionic gonadotropin (hCG) administration.Results A total of 2868 cycles were analysed. In day 3 embryo transfer cycles ( n = 2345), the clinical pregnancy rate was significantly higher in the normal P level group compared with the P elevation group (55.4% versus 46.7%, respectively) and the ectopic pregnancy rate was significantly lower in the normal P level group compared with the P elevation group (2.8% versus 7.9%, respectively). In day 5 blastocyst transfer cycles ( n = 523), there were no significant differences in the clinical pregnancy and ectopic pregnancy rates between the two groups, based on the P level.Conclusion These preliminary findings suggest that day 5 blastocyst transfer should be adopted for patients with P elevation on the day of hCG administration.