Live birth rate of twin pregnancies after frozen embryo transfer: natural cycle versus ovulation induction regimens.

ABSTRACT

PURPOSE: Ovulation induction (OI) using letrozole or human menopausal hormone (hMG) is recently developed for endometrium preparation in frozen embryo transfer (FET) cycles. The purpose of this study is to compare the live birth rate of twin pregnancies between modified natural and OI regimens for endometrium preparation in FET cycles. STUDY DESIGN: This study included all consecutive twin pregnancies following FET with modified natural cycle (mNC-FET) or OI (OI-FET) regimen for endometrium preparation between January 2015 to June 2019. Primary outcome was the live birth of at least one twin per pregnancy. Multivariable logistic regression analysis was used to evaluate the potential association of endometrium preparation regimen and live birth. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated. RESULTS: During the study period, 269 twin pregnancies after mNC-FET and 177 twin pregnancies after OI-FET were included. The live birth rate of at least one twin per pregnancy was not significantly different between mNC-FET and OI-FET groups, 92.2% vs 90.4%; aOR 0.65; 95%CI 0.32-1.34. The multivariable regression analysis showed that twin pregnancies after OI-FET had decreased odds for gestational diabetes mellitus (aOR 0.37; 95% CI 0.16-0.87) in comparison to twin pregnancies after mNC-FET. In subgroup analysis, we found that the rate of live birth of at least one twin per pregnancy was significantly higher in OI-FET cycles using letrozole compared to those using hMG (94% vs 83.3%; aOR 3.45; 95%CI 1.24-9.57). CONCLUSION: The live birth rate in twin pregnancies after FET is comparable between mNC or OI regimens for endometrium preparation.