Duration of ovarian stimulation is predictive of in-vitro fertilization outcomes

The aim of this study is to evaluate the effect of ovarian stimulation duration on oocyte/embryo development and pregnancy outcome in an in-vitro fertilization cycle (IVF).

Retrospective cohort study performed at University of South Florida reproductive center between January 2011 and December 2016. A total of 690 sub-fertile women who underwent autologous IVF cycle were included for analysis. The outcomes were compared between patients undergoing ovarian stimulation for ≤8 days and >8 days. Data was further categorized into accelerated stimulation group (≤8 days), normal duration stimulation group (9-12 days), and delayed stimulation group (≥13 days). Primary outcome was live birth rate. Secondary outcomes include oocyte development and embryo characteristics.

A total of 69 (10%) and 621 (90%) patients underwent ovarian stimulation for ≤8 and >8 days, respectively. Ovarian stimulation for >8 days had 2.1 times higher odds of live birth (35.7% vs. 20.8%, 95% CI: 1.02-4.44, P=0.04), and 1.9-fold-higher odds of clinical pregnancy (42.6% vs. 27.1%, 95% CI: 1.03-3.87, P=0.05). Number of matured oocytes (P=0.002), normally fertilized embryos (P=0.008), 6-8 cell stage embryos (P=0.003) and blastocysts (P=0.014) were higher in cycles with stimulation >8 days. Further analysis showed that live birth rate was highest in the group of patients with normal duration stimulation group (37.3%) compared to patients with delayed stimulation (25%) and accelerated stimulation (20.8%).

In an IVF cycle, optimal ovarian response and pregnancy outcome is associated with stimulation duration of at least 9 days. Both accelerated and delayed follicular recruitment are indicators for suboptimal response.