Does Earlier Administration Of Human Chorionic Gonadotropin (hCG) Improve The Probability Of Pregnancy In Cycles Stimulated With Rec-FSH AND GnRH Antagonists? A Prospective Randomized Trial

Progesterone elevation has been associated with prolongation of the follicular phase in GnRH antagonists cycles by two days after the commonly used criterion of the presence of at least three follicles of >or= 17 mm has been met. Such an intervention is associated with significantly lower ongoing pregnancy rates in GnRH antagonist cycles, without an apparent deterioration of embryo quality.

The adverse effect of P elevation on the day of hCG administration might be explained by the induction of differences at the histological level as well as at the gene expression level between endometrial samples exposed to varying concentrations of progesterone (P). Prolongation of follicular phase by delaying hCG administration for two days is associated with a higher incidence of endometrial advancement on the day of oocyte retrieval in GnRH antagonist cycles (Kolibianakis et al., 2005). Moreover, Vaerenbergh et al., (2011) demonstrated a distinct difference in endometrial gene expression profile between patients with progesterone serum concentration above and below the threshold of 1.5 ng/ml on the day of HCG administration.

Due to the fact that earlier triggering of final oocyte maturation is expected to result in lower progesterone levels on the day of hCG administration it might be assumed that such an intervention might result in an improved probability of pregnancy by leading to a less deranged and more receptive endometrium.

The purpose of this randomized controlled trial is to evaluate whether triggering of final oocyte maturation as soon as ≥ 3 follicles ≥ 16mm are present on ultrasound or one day later affects the probability of pregnancy in patients stimulated with rec-FSH/GnRH- antagonists for IVF.