Ganirelix acetate causes a rapid reduction in estradiol levels without adversely affecting oocyte maturation in women pretreated with leuprolide acetate who are at risk of ovarian hyperstimulation syndrome.

Background: Elevated estradiol (E(2)) levels predispose to development of ovarian hyperstimulation syndrome (OHSS). Since GnRH antagonist is associated with a reduction in E(2) levels, we hypothesized that GnRH-antagonist treatment of women down-regulated with GnRH agonist who are at risk of OHSS might reduce E(2) levels and avoid cycle cancellation.

Methods: Retrospective study in a university-based assisted reproduction technology (ART) programme in 87 patients treated with long luteal (LL) or microdose flare (MDF) with ovarian hyperresponse and 87 control patients without ovarian hyperresponse. GnRH-antagonist (ganirelix acetate) treatment was started and leuprolide acetate discontinued in women who failed to respond to a reduction in gonadotrophin dosage.

Results: In the treatment group, there was a significant, reproducible reduction in serum E(2) levels. Mean E(2) at the start of ganirelix treatment was 4219.8 pg/ml and decreased in 24 h to 2613.7 pg/ml (36.7%; P < 0.001). An average of 24.9 +/- 8.8 oocytes were obtained at retrieval and an average of 19.1 +/- 8.0 were metaphase II (79.2%). Fertilization occurred in 13.9 +/- 8.1 embryos (72.8%). In this high risk group, two cases of severe OHSS (2.3%) occurred. The ongoing pregnancy rate was 51.8%. Compared with the control group, there were no statistically significant differences in the rate of oocyte recovery, oocyte maturity, 2PN rate, fertilization, cancellation, OHSS or pregnancy.

Conclusions: GnRH-antagonist treatment of women pretreated with GnRH agonist rapidly reduced circulating serum E(2) without adversely affecting oocyte maturation, fertilization rates or embryo quality and resulted in a high pregnancy rate in this subgroup of patients at risk of OHSS.