The Effect of Luteal Blood Progesterone Levels on Ongoing Pregnancy Rates

Progesterone (P4) is essential for the secretory development of endometrium and the maintenance of early pregnancy. In the luteal phase following controlled ovarian stimulation in in vitro fertilization (IVF) treatment, P4 profile is completely different from natural cycles (Fauser, 2002). Since the optimal luteal P4 levels are not well known, in normal IVF treatment a standard regime of exogenous P4 is given without considering the ovarian response for stimulation and the steroid levels in luteal phase. In 2005 Humaidan et al, showed that following the fresh embryo transfer, low luteal P4 levels (39 nmol/l) has a negative impact on ongoing pregnancy rates (Humaidan, 2005). In the following randomized controlled trials (RCTs), the use of exogenous human chorionic gonadotropin (hCG) after gonadotropin releasing hormone (GnRH) agonist trigger as a luteal phase support (Humaidan, 2010, 2013), the mid luteal P4 levels increased to 77-409 nmol/l and birth rates per transfer raised to %24. In the light of these, it is essential that the progesterone levels in luteal phase is above the certain threshold for induction of the normal secretory development of endometrium following the IVF treatment and for the maintenance of pregnancy. The implantation window is defined as that period when the uterus is receptive for implantation of the free-lying blastocyst. For maximal effectiveness of assisted reproductive technologies in women, it is important to know the optimal time for embryo transfer which implies a need to predict the period of uterine receptivity. Blood progesterone levels can be an indirect indication for implantation window and the embryo transfer timing. In a recent study by Vuong et al., marked inter-personal variation in early luteal circulating P4 levels have been reported following the same hCG trigger dose; since a freeze-all policy was adopted in that study, the inter-personal variation during the early luteal phase was entirely caused by differences in