Synchronous and Asynchronous Blastomere Cleavage at Cryopreservation: Effect on Subsequent Embryo Survival, Pregnancy and Live Birth Rates

Abstract

Capsule: Although embryos with synchronous blastomere cleavage showed higher post-thaw survival rates, pregnancy rates did not differ. Thus, embryos with all cleavage patterns may be safely cryopreserved. Objective: To compare post-thaw embryo survival, pregnancy and live birth rates of embryos with synchronous vs asynchronous blastomere cleavage in frozen embryo transfer (FET) cycles. Design: Retrospective study. Setting: University-affiliated IVF unit. Patients: One thousand and sixty FET cycles performed from 2004-2006. Interventions: Cycles were divided into 3 groups: 1: cycles in which only embryos with synchronous blastomere cleavage were frozen; 2: cycles in which only embryos with asynchronous blastomere cleavage were frozen; 3: cycles in which both embryos with synchronous and asynchronous blastomere cleavage were frozen. Clinical and laboratory data were recorded and analyzed. Main Outcome Measures: Post-thaw embryo survival, morphologic grading, pregnancy and live birth rates. Results: A total of 1863 embryos were analyzed. Synchronous embryos had higher blastomere survival rates and morphological grading at thawing. Pregnancy and birth rates did not differ among groups. In a multivariant logistic regression analysis, a number of transferred embryos and embryo morphological grading at thawing were the only parameters that affected pregnancy and live birth rates. Conclusions: Embryos with both synchronous and asynchronous blastomere cleavage can be selected by classical embryo grading and safely cryopreserved.