Natural cycle for frozen-thawed embryo transfer: Spontaneous ovulation or triggering by HCG

Objective. - To compare frozen-thawed embryo transfer (FET) outcomes in natural cycles according to ovulation induction: spontaneous versus recombinant human chorionic gonadotrophin (r-hCG) triggering. Methods. - This retrospective study included all patients monitored for natural cycle FET during one year. When serial monitoring were performed until spontaneous LH rise, patients were included in group A (n = 38) whereas those receiving r-hCG for ovulation triggering formed group B (n = 43). All embryos I had been cryopreserved by a vitrification method following a previous IVF cycle. No luteal phase support had been given. We compared outcomes between the 2 groups. Results. - After checking groups comparability, we didn't find significant difference for the implantation rate, clinical pregnancy rate and live birth (31% vs 45%, 32% vs 51% et 21% vs 32%, respectively for group A and B). The number of monitoring was significantly lower in group B (1,9 + 0,8 versus 2,5 1, P = 0,006). Discussion. - Although no consensus has been yet established, natural cycle seems indicated for normoovulating patients but the question of ovulation induction is still debated. In our study, triggering ovulation by r-hCG, respecting strict criteria, seems provide good results while reducing both protocol's constraints and cost. (C) 2018 Elsevier Masson SAS. All rights reserved.