Clinical And Perinatal Outcomes Of Fresh Single-Blastocyst-Transfer Cycles Under An Early Follicular Phase Prolonged Protocol According To Day Of Trigger Estradiol Levels

Backgroud: This study's objectives were to compare the clinical, perinatal, and obstetrical outcomes of patients with different estradiol (E2) levels in fresh single-blastocyst-transfer (SBT) cycles under an early follicular phase prolonged regimen on the day of trigger.Methods: We recruited patients in fresh SBT cycles (n = 771) undergoing early follicular phase prolonged protocols with beta-hCG values above 10 IU/L between June 2016 and December 2018. Patients who met the inclusion and exclusion criteria were divided into four groups according to their serum E-2 level percentages on the day of trigger: <25th, 25th-50th, 51st-75th, and >75th percentile groups.Results: Although the rates of clinical pregnancy (85.57% (166/194)), embryo implantation 86.60% (168/194), ongoing pregnancy (71.13% (138/194)), and live birth (71.13% (138/194)) were lowest in the >75th percentile group, we did not observe any significant differences (all P > 0.05). We used this information to predict the rate of severe ovarian hyperstimulation syndrome (OHSS) area under the curve (AUC) = 72.39%, P = 0.029, cut off value of E-2 = 2,893 pg/ml with the 75% sensitivity and 70% specificity. The 51st-75th percentile group had the highest rates of low birth weight infants (11.73% (19/162), P = 0.0408), premature delivery (11.43% (20/175), P = 0.0269), admission to the neonatal intensive care unit (NICU) (10.49% (17/162), P = 0.0029), twin pregnancies (8.57% (15/175), P = 0.0047), and monochorionic diamniotic pregnancies (8.57% (15/175); P = 0.001). We did not observe statistical differences in obstetrics complications, including gestational diabetes mellitus (GDM), gestational hypertension, placenta previa, premature rupture of membranes (PROM), and preterm premature rupture of membranes (PPROM).Conclusion: We concluded that serum E-2 levels on the day of trigger were not good predictors of live birth rate or perinatal and obstetrical outcomes. However, we found that high E-2 levels may not be conducive to persistent pregnancies. The E-2 level on the day of trigger can still be used to predict the incidence of early onset severe OHSS in the fresh SBT cycle.