O-247 Pregnancy and live birth rates in first blastocyst transfer: Fresh versus frozen -An individual patient data meta-analysis based on randomised controlled trials with follitropin delta

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Abstract Study question How does frozen blastocyst transfer compare to fresh blastocyst transfer, when evaluating pregnancy and live birth in the first transfer following follitropin delta treatment? Summary answer In low and normoresponders, live birth rate (LBR) was similar with fresh and frozen transfer. In high responders, LBR was significantly higher with frozen transfer. What is known already Frozen embryo transfer has increased significantly in recent years along with improved survival of cryopreserved embryos. Cryopreservation of all embryos (“freeze-all”) is commonly used following gonadotropin-releasing hormone (GnRH) agonist triggering in patients at risk of ovarian hyperstimulation syndrome (OHSS). Studies comparing success rates in fresh versus frozen transfer suggest improved live birth rate (LBR) with frozen transfer; however, this benefit is primarily observed for high responders. Previous publications on follitropin delta have focused on clinical outcomes after fresh transfer. Therefore, this study evaluates outcomes of fresh versus frozen transfer following follitropin delta stimulation. Study design, size, duration Individual patient data (IPD) meta-analysis on 4 randomised controlled trials. Patients who received follitropin delta for ovarian stimulation and underwent blastocyst transfer were included in the analysis (n = 1585). Pregnancy and live birth following the first blastocyst transfer after ovarian stimulation were compared between patients with fresh blastocyst transfer (n = 1303) and patients with frozen blastocyst transfer (n = 282) using the Mantel-Haenszel method. Subgroup analyses were performed based on age, AMH and number of oocytes retrieved. Participants/materials, setting, methods Participants were women, 18-42 years, undergoing their first or second IVF/ICSI cycle in a GnRH antagonist/agonist protocol. Depending on follicular development, triggering was either performed with human chorionic gonadotrophin followed by single/double blastocyst transfer on Day 5 in the fresh cycle, or, at high follicular response, with GnRH agonist followed by cryopreservation of all blastocysts (“freeze-all”) and single/double blastocyst transfer in natural or programmed frozen cycles. Pregnancies were followed until birth. Main results and the role of chance The mean age and BMI were similar in patients undergoing fresh transfer and patients undergoing frozen transfer (33.8±4.0 years versus 33.0±4.2 years, respectively, and 25.2±4.6 kg/m2 versus 26.1±5.0 kg/m2, respectively), whereas median baseline AMH level was higher in patients with frozen transfer (29.8 pmol/l) than patients with fresh transfer (15.2 pmol/l). In agreement with the “freeze-all” approach for high responders, patients with frozen transfer had significantly (p < 0.0001) more oocytes retrieved (mean 23.5 oocytes) than patients with fresh transfer (mean 10.5 oocytes). In the overall study population, significant differences were observed for ongoing pregnancy rate (40.4% versus 48.7% for fresh versus frozen transfer [p = 0.0173]) and live birth rate (LBR) (39.4% versus 47.4% for fresh versus frozen transfer [p = 0.0209]). In the subgroup analyses, significant differences in LBR were observed between fresh versus frozen transfer for patients with AMH ≥15 pmol/l (41.1% versus 49.5%, p = 0.0394) and patients with ≥15 oocytes retrieved (38.4% versus 53.4%, p = 0.0037), while no differences were observed for patients with AMH <15 pmol/l (37.4% versus 33.8%, p = 0.7081) or patients with 1-14 oocytes retrieved (38.8% versus 36.8%, p = 0.7767). No significant differences in LBR between fresh and frozen transfer were observed in either age group (<35 years or ≥ 35 years). Limitations, reasons for caution The majority of the patients with frozen blastocyst transfer as the first transfer after ovarian stimulation were patients with a high follicular response who underwent “freeze-all”. Data from low and normal responders undergoing frozen cycles are limited. Wider implications of the findings This IPD meta-analysis suggests that pregnancy and live birth rates from frozen blastocyst transfers are similar to those achieved with fresh transfers after follitropin delta stimulation. Increased ongoing pregnancy rate and LBR following frozen as compared to fresh transfer cycles was observed in patients with high ovarian response. Trial registration number Yes

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