International differences in IVF live birth rates and cumulative ongoing pregnancy rates following ovarian stimulation with corifollitropin alfa or recombinant FSH

Abstract

To report live birth rates following fresh embryo transfer (ET) and cumulative ongoing pregnancy rates (OPRs) from fresh or frozen-thawed embryo transfer (FTET) after a single ovarian stimulation (COS) cycle with corifollitropin alfa or rFSH in North American (NA) and European (EU) IVF units. Randomized, double-blind trial (Engage) involving 14 centers in NA (N = 804) and 20 in EU (N = 702). Patients >60 kg received a single dose of 150 μg corifollitropin alfa or daily 200 IU rFSH for the first 7 days of COS in a GnRH antagonist protocol. Implantation rates (IR) after corifollitropin alfa or rFSH treatment and fresh ET at day 3 were respectively 38.5% and 31.7% in NA vs 31.0% and 23.2% in EU. Both region (P<0.01) and treatment (P = 0.01) had a significant effect on IR. Accordingly, OPRs were 45.4% (182/401) and 45.7% (184/403) in NA and 31.5% (112/355) and 29.4% (102/347) in EU in corifollitropin alfa and rFSH groups, respectively. Live birth rates were 39.2% in each treatment group in NA and 31.5% and 28.8% in EU for corifollitropin alfa and rFSH group, respectively. The mean (SD) number of good-quality embryos in NA was 5.3 (4.6) and 5.1 (4.4) compared with 3.4 (3.7) and 3.5 (3.0) in EU for corifollitropin alfa and rFSH, respectively. The number of fresh embryos transferred for both treatment groups was 1.9 (0.3) in NA and 1.5 (0.5) in EU. Multiple PRs of 34.6% and 28.8% in NA compared with 17.9% and 12.7% in EU for corifollitropin alfa and rFSH, respectively. Cumulative OPRs including FTET were 53.1% (213/401) and 51.9% (209/403) in NA and 40.6% (144/355) and 36.9% (128/347) in EU for corifollitropin alfa and rFSH, respectively. IR significantly higher in NA than in EU and (cumulative) OPRs and live birth rates were also higher in NA than in EU. Possible explanations are a higher recovery of good-quality embryos, better embryo selection, and a higher frequency of double instead of single ET.