Blastocyst expansion score and trophectoderm morphology strongly predict successful clinical pregnancy and live birth following elective single embryo blastocyst transfer (eSET): a national study.

PURPOSE: To determine which characteristics of blastocyst embryo morphology may predict clinical pregnancy and live birth rates.

METHODS: A retrospective analysis of data from 3,151 cycles of fresh, non-donor eSET cycles from 2008 to 2009 was performed. Data were obtained from the Society for Assisted Reproductive Technologies (SART) underwent. All eSET were performed at the blastocyst stage. Main outcome measures were clinical pregnancy and live birth rates.

RESULTS: Trophectoderm morphology, embryo stage and patient age are highly significant independent predictors of both clinical pregnancy and live birth. Neither inner cell mass morphology nor embryo grade predicted clinical pregnancy or live birth.

CONCLUSIONS: Better trophectoderm morphology, younger patient age and further blastocyst progression all result in higher clinical pregnancy and live birth rates. Therefore, trophectoderm morphology and blastocyst stage should preferentially be used as the most important factors in choosing the best embryo for transfer.