The impact of preovulatory versus midluteal serum progesterone level on live birth rates during fresh embryo transfer

Background: Conflicting evidence still prevails concerning the effect of preovulatory elevated progesterone (EP4) on reproductive outcomes in fresh embryo transfer (ET). However, few studies have analyzed the effect of EP4 on the likelihood of pregnancy using multivariate regression approach. The potential confounding factors tested in these studies were limited to either patient’s characteristics or to stimulation related parameters. Yet, several studies have shown that postovulatory parameters such as midluteal progesterone (P4) level may be considered as a proxy variable of endometrial receptivity as well. Objective: The aim of the present study was to estimate the independent effect of preovulatory P4 effect, if any, on the probability of live birth (LB) by considering the midluteal endocrine profile when controlling for the potential confounding factors. Methods: This is a secondary data analysis of a cohort of fresh IVF/ICSI cycles triggered with GnRH agonist (n = 328) performed in a single IVF center during the period 2014–2016. Patients contributed only one cycle and were stratified into four groups according to preovulatory P4 quartiles. We assessed the association between preovulatory P4 and the odds of LB calculated by logistic regression analysis after controlling for the most clinically relevant confounders. The primary outcome measure: Live birth rates (LBR). Results: Both preovulatory and midluteal P4 were significantly correlated with the ovarian response. Logistic regression analysis showed that preovulatory serum P4 did not have a significant impact on LBR. In contrast, midluteal serum P4 level was an important independent factor associated with LBR. The optimal chance of LBR was achieved with midluteal serum P4 levels of 41–60 ng/ml, [OR: 2.73 (1.29–5.78); p