Shorter Length of Gonadotropin Stimulation is Associated with Adverse IV F outcomes: A Retrospective Analysis

Background: The impact of the length of gonadotropin stimulation (LOS) on IVF outcome has been studied by several groups. Results so far have been conflicting. The primary aim was to evaluate the impact of LOS on pregnancy rates and oocyte yield. Secondary outcomes included comparison of outcome based on LOS separately in gonadotropinreleasing hormone (GnRH) agonist (GnRH-a) and antagonist (GnRH-ant) cycles. Methods: Retrospective review of IVF cycles managed by a single provider in a private clinic. Data was collected for demographic, stimulation, embryology and clinical outcome parameters. Oocyte yield (the ability to obtain an oocyte from a proper sized follicle) was calculated for each cycle (number of oocytes retrieved/ follicles >14 mm at last scan). LOS was divided into short (≤8 days), normal (9-12 days), and prolonged (≥13 days). Student’s t-test, ANOVA, and Chi-Square tests were used. Results: Outcome based on 295 IVF cycles (GnRH-a: 94 and GnRH-ant: 201) were analyzed. Overall pregnancy rate (PR) was 36.3%. Age, ovarian reserve, number of available and transferred embryos didn’t differ in the three groups. Shorter cycles compared unfavorably to normal and prolonged stimulations regarding oocyte yield (1.2 vs 1.5 vs 1.9, P<0.05) and PR (17.6% vs 40.9% vs 28.7%, P<0.05). Oocyte yield was significantly lower in cycles ≤8 days in both the GnRH-a and GnRH-ant groups when compared to longer stimulation. Conclusions: Quicker response to gonadotropin stimulation may suggest diminished ovarian reserve but could indicate inadequate time for oocyte/ endometrial maturation to occur. LOS should be considered prior to hCG trigger administration.