Elevated serum estradiol levels on embryo transfer day predict higher pregnancy success in HRT-FET cycles
摘要
To investigate the association between serum estradiol (E2) levels on the day of embryo transfer and clinical pregnancy outcomes in hormonally prepared frozen–thawed embryo transfer (HRT-FET) cycles with optimal progesterone (P4) levels.
MethodsIn this retrospective study, 175 HRT-FET cycles conducted between January and May 2024 were analyzed. Serum E2 and P4 levels were measured on the first and fourth days of progesterone administration. A decision tree analysis identified the optimal E2 threshold for embryo transfer day, dividing patients into two groups based on this cut-off. Clinical pregnancy and early pregnancy loss rates were compared between the groups. Binary logistic regression was performed to evaluate the relationship between E2 levels and pregnancy outcomes.
ResultsA serum E2 threshold of 201 pg/mL on embryo transfer day was identified. Patients with E2 > 201 pg/mL had significantly higher clinical pregnancy rates (62.6% vs. 2.6%, p < 0.001) and significantly lower early pregnancy loss rates (7.25% vs. 87.5%, p < 0.001). Logistic regression confirmed a significant positive association between higher serum E2 and clinical pregnancy rates.
ConclusionSerum estradiol levels above 201 pg/mL on the day of embryo transfer are independently associated with significantly improved pregnancy outcomes, including higher clinical pregnancy rates and lower early pregnancy loss, in HRT-FET cycles. These findings highlight the potential value of E2 monitoring as a complementary tool to optimize embryo transfer timing and enhance the success of hormonally prepared frozen embryo transfer protocols.
Graphical Abstract