Purpose: To assess the importance of each blastocyst morphological criteria with pregnancy and perinatal outcomes.
Methods: This single-center retrospective cohort study included blastocyst single embryo transfers (SET) performed between 1/2012-2/2018. Poisson regression was used to evaluate pregnancy outcomes following fresh and cryopreserved embryo transfer (CET) for association with blastocyst expansion, inner cell mass (ICM) quality, and trophectoderm (TE) quality. Among cycles resulting in live birth, associations with preterm birth, small for gestational age (SGA) and large for gestational age (LGA), were evaluated using logistic regression.
Results: A total of 1023 fresh and 1222 CET cycles were included, of which 465 (45.1%) fresh and 600 (48.5%) CET cycles resulted in singleton live birth. Clinical pregnancy rates increased with increasing expansion among fresh transfers (p for trend = 0.001) but not CET (p = 0.221), and with TE quality for both fresh and CET cycles (p = 0.005 and < 0.0001, respectively). Live birth rates increased with increasing expansion (fresh p = 0.005, CET p = 0.018) and TE quality (fresh p = 0.028, CET p = 0.023). ICM grade was not associated with pregnancy outcomes; however, higher ICM quality among CET cycles was associated with increased chance of preterm birth (p = 0.005).
Conclusions: In blastocyst SET, blastocyst expansion and TE quality were each associated with clinical pregnancy and live birth. While higher ICM quality was associated with increased chance of preterm birth among CET, no other associations with perinatal outcomes were identified. Clinicians can be reassured that pregnancies from blastocysts with lower expansion, ICM, or TE qualities are not more likely to result in adverse perinatal outcomes.
Keywords: Birthweight; Blastocyst morphology; In vitro fertilization; Perinatal outcomes; Preterm birth.