Effects of Different Exposure Days to Gonadotropin-Releasing Hormone Agonist (GnRH-a) on Live Birth Rates in the Depot GnRH-a Protocol: A Retrospective Analysis of 7007 Cycles.

BACKGROUND In controlled ovarian hyperstimulation protocols worldwide, depot gonadotropin-releasing hormone agonist (GnRH-a) pretreatment is generally used for pituitary desensitization. The delay between the GnRH-a administration and starting gonadotropin treatment varies greatly, from 25 to 60 days. However, the association between exposure days to GnRH-a before the onset of gonadotropin administration and the clinical outcomes remains unknown. MATERIAL AND METHODS This retrospective study included 7007 patients who underwent fresh embryo transfers between February 2016 and July 2019. The duration of pituitary downregulation was categorized into 3 groups: group 1, ≤30 days; group 2, 31-35 days; and group 3, ≥36 days. The rates of live birth were compared as the main outcome measure. Logistic regression analysis was also performed after controlling for a range of confounders. RESULTS The number of patients in groups 1, 2, and 3 was 2001, 2824, and 2182, respectively. Group 3 (≥36 days) had a noticeably higher live birth rate (48.1%) than the other 2 groups (42.6% and 43.9%, P=0.001). The rate of live birth was remarkably enhanced in group 3 (adjusted odds ratio: 1.264, 95% confidence interval: 1.098, 1.455, P=0.001) after controlling for confounders, while the difference was not found in group 2 (P=0.512) compared with group 1. CONCLUSIONS In the depot GnRH-a protocol, live birth rates are higher among patients needing a longer time to achieve the goal of pituitary downregulation.