Does Estradiol Orally and Vaginally Administered Together Impact Live Birth and Neonatal Outcome in Artificial Frozen-thawed Embryo Transfer Cycles: A Retrospective Cohort Study

Abstract Background: Previous studies have demonstrated that newborns from fresh embryo transfer are with higher risk of small for gestation (SGA) rate than those from frozen-thawed embryo transfer (FET). It is suggested that supraphysiologic serum estradiol in controlled ovarian stimulation (COS)is one of reasons. Out study aims to investigate whether exogenous estradiol delivered regimens have an impact on live birth rate and singleton birthweight in hormone replacement (HRT)-FET cycles.Methods:This retrospective study involved patients undergoing their first FET with HRT endometrium preparation followed by two cleavage-staged embryos transfer, comparing orally and vaginal estradiol tablets (OVE) group versus oral estradiol tablets (OE) group from January 2015 to December 2018 at our center. A total of 792 patients fulfilled the criteria, including 282 live birth singletons. Live birth was the primary outcome. Secondary outcome included clinical pregnancy rate, singleton birthweight, large for gestational age (LGA) rate, SGA rate, preterm delivery rate. Results:Patients in OVE group achieved higher serum estradiol level with more days of estradiol treatment. No difference in live birth (Adjusted OR 1.327; 95%CI 0.982, 1.794, p=0.066) and clinical pregnancy rate (Adjusted OR 1.278; 95%CI 0.937, 1.743, p=0.121) was found between OVE and OE groups. Estradiol route did not affect birth weight (β=-30.962, SE=68.723, p=0.653), the odds of LGA (Adjusted OR 1.165; 95%CI 0.545, 2.490, p=0.694), the odds of SGA (Adjusted OR 0.569; 95%CI 0.096, 3.369, p=0.535) or the preterm delivery rate (Adjusted OR 0.969; 95%CI 0.292, 3.214, p=0.959).Conclusion:Estrogen orally and vaginally together did not have an impact on clinical outcomes and singleton birthweight compared to estrogen orally taken, but was accompanied with relative higher serum E2 level and potential maternal undesirable risks.