The Developmental Stage at Cryopreservation in Assisted Reproduction: A Systematic Review and Meta-Analysis of Pregnancy Outcomes

Abstract

Jason Yen-Ping Ho, Andrew Chao-Hung Lai

To date, there is no consensus in embryo developmental stages for cryopreservation. The present study aimed to investigate the impact of embryo developmental stages at cryopreservation on pregnancy outcomes of frozen embryo transfer. Systematic review and meta-analysis of relevant studies identified through MEDLINE literature search was performed. The primary outcome was live birth/delivery rate, and the secondary outcomes included implantation rate, ongoing pregnancy rate, clinical pregnancy rate, miscarriage rate, and multiple pregnancy rate. The protocol of this systematic review has been registered on PROSPERO 2017 (registration number: CRD42017072828). Five studies met the eligibility criteria were included in the present review. The outcomes of embryos frozen at different stages but transferred at the same stage were analyzed and compared. Embryos frozen at non-blastocyst showed a significant higher delivery/live birth rate than those cryopreserved at blastocyst (odds ratio=1.37; 95% confidence interval, 1.13-1.66) in the setting of frozen embryo transfer with blastocysts. There was only a limited number of studies with analyzable data for comparisons. The literature varied substantially in study design and methodology applied. Although a significant difference was observed toward an improved delivery/live birth rate for blastocyst transfer with embryos frozen at non-blastocyst stage, future studies are required to further corroborate this finding.

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