O-005 The ToF-study - comparing the cumulative live birth rate of blastocyst-stage versus cleavage-stage embryo transfers in good prognosis IVF patients: a multicenter randomized controlled trial.

Abstract Study question Does blastocyst-stage embryo transfer in fresh and frozen cycles improve the cumulative live birth rate (cLBR) compared with cleavage-stage IVF/ICSI treatments? Summary answer In good prognosis IVF patients (≥4 available embryos), a policy did not result significant higher cLBR to policy. What is known already A recent Cochrane systematic review meta-analysis concluded that treatments associated rates of pregnancy comparison embryos. However, it unknown whether blastocyst-transfer also improves rate, i.e. derived from frozen-thawed transfers following single oocyte retrieval, IVF/ICSI. design, size, duration this multicenter randomized controlled trial women were randomly allocated (blastocyst group - on day 5 after retrieval followed by vitrification remnant blastocysts 6 local criteria) or (cleavage-stage 3 cryopreservation 4). Randomization was stratified for age (≥36 < 36 years). Participants/materials, setting, methods Women (defined as presenting ≥4 embryos 2 culture), during their first, second, third treatment cycle, included. The primary outcome per including within 12 months randomization (or 17 COVID pandemic). Risk ratios (RR) 95% CI adjusted calculated using log-linear binominal regression. Main results role chance total 1202 21 Dutch centers assigned (N = 599) cleavage stage 603) between 2018 2021. At submission abstract, data 1153 (95.9%) women, 577 576 group. 58.2% (336/577 women) 57.3% (330/576 (RR 1.022, 0.844-1.237; p 0.825). 38.0% (219/577 versus 29.9% (172/576 respectively 1.282, 1.017-1.615 0.035). Interaction found years older blastocyst Analyses other outcomes, obstetrical neonatal patient burden, cost effectiveness are ongoing. Limitations, reasons caution Outcomes only applicable at least four two culture. Wider implications findings treatments. Further research into interaction outcomes warranted. Trial registration number NTR7034