Advantages of cumulative pregnancy outcomes in freeze-all strategy in high responders – A case-control matching analysis of a large cohort

Abstract

Background/Purpose: The freeze-all strategy in high responders is considered to be a safe and effective strategy for in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) treatment; however, the cumulative pregnancy outcomes have not been established. Methods: A retrospective, single-center cohort study was conducted and 1311 high-responder patients (>20 oocytes retrieved and/or a serum estradiol level > 3000 pg/ml on the triggering day) were recruited from 2006 to 2015. The study group (n = 351) underwent the freeze-all strategy with subsequent thawed embryo transfer (ET), and the control group (n = 960) received fresh-cycle ET and subsequent thawed ET if needed. A case-control matching analysis was performed to match the two groups for the number of retrieved oocytes. The primary outcomes were the ongoing pregnancy rate (OPR) of the first ET cycle and the cumulative OPR. Results: After matching, there was a significantly higher OPR in the first ET cycle (49.5% vs. 32.2%, p < 0.0001; n = 301 in each group) and the cumulative OPR (69.4% vs. 55.1%, p < 0.0001) in the study group, with significantly fewer total transferred embryos and cycles. The advantages of the freeze-all strategy for the OPR in the first ET cycle (OR: 1.97, p < 0.0001) and the cumulative OPR (OR: 1.49, p = 0.032) remained statistically significant after adjusting for other possible confounding factors in multivariate logistic regression analysis. Conclusion: For high responders, the freeze-all strategy with thawed ET achieved a significantly higher OPR in the first ET cycle and a higher cumulative OPR than the fresh ET strategy. Keywords: Assisted reproductive technology, Embryo transfer, Freeze-all, Ongoing pregnancy rate, Vitrification