Blastocyst development rate influences singleton gestational age of similarly graded blastocysts after vitrified–warmed single embryo transfer cycles

Abstract

Research questionDoes the development rate of blastocysts influence neonatal outcomes after blastocyst transfer cycles when the morphological score of the transferred blastocysts is similar? DesignA retrospective study involving singleton live births born to 1280 women undergoing single frozen blastocyst transfers (FBTs) between January 2016 and December 2018 at a tertiary care centre. Patients were grouped into day-5 or day-6 groups depending on the development rate of blastocysts. These were further grouped into four groups based on the blastocyst inner cell mass and trophectoderm scoring: excellent (AA); good (AB or BA); average (AC, CA or BB); and poor (BC or CB). The primary outcomes were gestational age and singleton birth weight. ResultsSingletons resulting from day-5 single FBT were at a lower risk of preterm birth than those resulting from day-6 single FBT (adjusted OR 0.63, 95% CI 0.41 to 0.97, P = 0.035). In the day-5 good-quality blastocyst group and day-5 average-quality blastocyst group, singletons were at a lower risk of preterm birth than those resulting from day-6 groups, respectively (adjusted OR 0.22, 95% CI 0.08 to 0.63, P = 0.005 and adjusted OR 0.52, 95% CI 0.29 to 0.94, P = 0.03). ConclusionsDay-6 single FBT was associated with a higher risk of preterm birth compared with day-5 single FBT in good and average morphological scoring blastocysts. Our analysis was restricted to women with singleton births from single FBTs. Future prospective studies are required to confirm the findings.