Endometriosis is common in women referred for infertility. In vitro fertilization provides good results but the choice of the best-controlled ovarian hyperstimulation protocol remains a subject of debate. The objective of this retrospective study was to compare pregnancy outcomes in women with endometriosis-associated infertility after COH with a long agonist protocol or a six-week oral contraception-antagonist protocol.

Retrospective analysis of a prospective database identified 284 COH cycles – 165 with GnRH-agonist protocol (GnRH-agonist group) and 119 with GnRH-antagonist protocol (GnRH-antagonist group) – in 218 women, with endometriosis from January 2013 to October 2015.

No difference in the epidemiological characteristics was found between the groups. Per started cycle, pregnancy and live-birth rates after fresh embryo transfer were higher with the GnRH-agonist protocol (25% vs. 13%, P=0.02 and 18% vs. 8%, P=0.04, respectively). Considering analysis per cycle with embryo transfer, the pregnancy rate was similar in both groups while the live-birth rate was higher in the GnRH-agonist group (29% vs. 17%, P=0.053 and 22% vs. 10%, P=0.02, respectively). No difference was observed between the groups with freeze-thaw embryo transfer. Subgroup analysis (endometrioma alone, deep infiltrating endometriosis with and without endometrioma, endometriosis with and without adenomyosis) revealed no difference between the groups for either pregnancy or live-birth rates.

A GnRH-agonist protocol appears to result in higher pregnancy and live-birth rates after fresh embryo transfer in women with endometriosis-associated infertility, suggesting that a GnRH-antagonist protocol might negatively impact endometrial receptivity.