Progesterone-modified natural cycle preparation for frozen embryo transfer

Research question

Is there any difference in clinical outcomes between the progesterone-modified natural cycle (P4mNC) and hormone replacement therapy (HRT) endometrial preparation protocols after single euploid blastocyst frozen embryo transfer (FET) cycles?

Design

A retrospective cohort study was performed at a single, private, high-volume fertility centre. Patients who underwent single euploid blastocyst FET between January 2017 and December 2019 were included. A total of 1933 FET cycles were reviewed, and 723 FET cycles from 548 patients met the inclusion criteria. Two groups were compared according to endometrial preparation: 327 P4mNC-FET and 396 HRT-FET cycles. The primary outcome was the live birth rate. The secondary outcomes included the clinical pregnancy rate and the miscarriage rate.

Results

There were no differences in the clinical pregnancy rate (50.2% versus 47.0%, P = 0.688), miscarriage rate (9.8% versus 14.5%, P = 0.115) and live birth rate (45.0% versus 39.6%, P = 0.331) between the P4mNC-FET and HRT-FET groups after covariate adjustments.

Conclusions

There were no differences in the clinical outcomes between the P4mNC-FET and HRT-FET cycles. These results indicate that P4mNC-FET cycles produce clinical outcomes comparable to those of more traditional HRT-FET while allowing greater flexibility in the timing of embryo transfer.