Effect of re-cryopreservation on pregnancy and neonatal outcomes: Analysis using propensity score matching

Objective: To comprehensively assess the effect of re-cryopreservation procedure on pregnancy and neonatal outcomes by using propensity matching (PSM) analysis. Methods: The patients were divided into two groups according to the times of embryo cryopreservation: the cryopreservation group (n = 8034) and the re-cryopreservation group (n = 66). To optimize the precision of the present study, we used PSM to adjust the different baseline characteristics between the two groups, including maternal age, the number of good-quality embryos transferred and endometrial preparation protocols. The primary outcome was live-birth rate. The secondary outcomes were biochemical pregnancy rate, clinical pregnancy rate, and miscarriage rate. Results: We found that the rates of biochemical pregnancy and clinical pregnancy were comparable between the two groups, whereas miscarriage rate was increased, resulting in significantly reduced live-birth rate in the re-cryopreservation group. No differences were observed in terms of neonatal outcomes, including cesarean section, birth weight, and malformation as well as pregnancy complications. Moreover, multivariable analysis demonstrated that re-cryopreservation was an independent risk factor for live-birth rate. Conclusion: The present study demonstrated the adverse effect of re-cryopreservation on pregnancy outcomes, providing valuable information for clinical decision making and patient counseling.