Endometrial thickness dynamics and morphologic characteristics during pituitary downregulation with antagonists in assisted reproductive technology cycles.

Objective: The purpose of this study was to evaluate whether the dynamics of endometrial stripe thickness during gonadotropin-releasing hormone (GnRH) antagonist pituitary downregulation in in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles are related to implantation and pregnancy outcomes.

Methods: This retrospective cohort study evaluated 115 conventional IVF/ICSI cycles. All patients underwent ovarian stimulation with gonadotropins and the GnRH antagonist ganirelix acetate. The endometrial stripe was measured transvaginally daily from the day of initial GnRH antagonist administration to the day of the human chorionic gonadotropin (hCG) trigger and then transabdominally on the day of embryo transfer. We created 5 categories (0-4) of endometrial thickness variation, considering significant a daily variation of 1.5 mm. Our aim was to predict whether the endometrial thickness dynamics or morphologic characteristics were related to the duration of ovarian stimulation, duration of ganirelix use, or estradiol levels during ovarian stimulation and whether they would influence implantation and pregnancy rates.

Results: No relationship was found between the duration of ovarian stimulation, duration of ganirelix use, and estradiol level (expressed as the area under the curve), and endometrial thickness dynamics or morphologic characteristics. Despite a thinner endometrial thickness in 37% of the cycles on the day of the hCG trigger compared with the beginning of GnRH antagonist stimulation, there was no correlation between endometrial dynamics and pregnancy outcomes. There was, instead, a positive relationship between a trilaminar endometrial morphologic pattern with a positive pregnancy test result, successful implantation, and ongoing pregnancy (P < .05).

Conclusions: Despite a net decrease in thickness in almost 50% of cases, endometrial dynamics did not correlate with pregnancy outcomes. Conversely, a trilaminar endometrial morphologic pattern on the day of embryo transfer was positively related to pregnancy outcomes.