OPTIMAL DURATION OF ESTROGEN PRIMING DURING FROZEN EMBRYO TRANSFER (FET) CYCLES: DOES IT REALLY MATTER?

Based on the fact that follicular phase of menstrual cycle is variable in length, it has been assumed duration estrogen (E2) priming could also be variable. A controversy emerged however between studies indicating an extended E2 only treatment alters ART outcomes and others challenged such effect. Therefore, we conducted our own analysis to further determine impact following single frozen blastocyst transfers progesterone cycles. Retrospective cohort study. Patients <40 years age undergoing Frozen Embryo Transfers (FET) after their first autologous IVF center 01/2017 12/2019 were analyzed. We considered patients with a morphologically normal uterus hysterosonogaphy and/or hysteroscopy. excluded endometrial thickness <7 mm administration. Endometrial preparation was achieved using oral (4mg BID) addition combination subcutaneous vaginal progesterone. Single transfer performed 6th day exposure. The primary endpoint livebirth rate (LBR) secondary endpoints included implantation (IR), clinical pregnancy (CPR) early loss rates as well infant birthweight. administration LBR, CPR, IR assessed multivariable logistic regression models, adjusting for age, body mass index, thickness, development embryo morphology grade. Effect birthweight linear regression. (mean: 16.3; range: 10-39days) before FET did not affect (odds ratio [OR] = 0.994, 95% confidence interval CI [0.960; 1.030]), (OR= 0.99, 95%CI [0.93; 1.01]), (OR=1.05, [0.854; 1.10]), live birth 1.016, [0.980; 1.054]). Also, exposure (in grams) (r= -0.04, p=0.4415). Our findings suggest variation supplementation initiation does outcome transfers, including weight.