P–772 Blastocyst quality and perinatal outcomes in women undergoing single blastocyst transfer in frozen cycles

Abstract Study question Is the morphological grading systems of a blastocyst associated with perinatal outcomes in women undergoing frozen-thawed single blastocyst transfer (SBT)? Summary answer Preferential transfer of a blastocyst based on their morphological grading systems appears to be supported by observed differences in perinatal outcomes. What is known already The transfer of a morphologically good quality blastocyst is associated with higher implantation and pregnancy rates as compared with a poor quality blastocyst. However to date, the association of the morphologic parameters of the blastocyst (developmental stage, inner cell mass (ICM), and trophectoderm (TE)) with the perinatal outcomes after blastocyst transfer remains unknown. Study design, size, duration A retrospective cohort study including 21,648 frozen-thawed SBT cycles from January 2013 to March 2019. Participants/materials, setting, methods 6037 women with singleton delivery in Peking University Third Hospital were eligible for analysis. Multivariate logistic regression was used to test the risk of factors with the expression of crude odds ratios (OR) and adjusted OR (aOR) with 95% confidence intervals (CI). Main results and the role of chance Transfer of a blastocyst with grading lower than 3BB was associated with a higher chance of female baby (49% vs 43%, aOR = 1.27 (1.12, 1.43)) and a higher rate of cesarian section (C-section) (69% vs 65%, aOR = 1.17 (1.03, 1.34)). Compared with stage 4 blastocyst, transfer of a stage 3 blastocyst was associated with a higher chance of preterm delivery (PTD) (aOR = 1.77 (1.08, 2.90)). Both stage 3 and stage 6 blastocyst transfer was associated with a lower chance of female baby (aOR = 0.68 (0.48, 0.97), 0.66 (0.47, 0.93), respectively). Compared with grade A ICM blastocyst transfer, Grade B ICM and grade C ICM blastocyst transfer was associated with a lower chance of a female baby (adjusted OR = 0.84 (0.73, 0.96), 0.63 (0.48, 0.83), respectively) and a higher risk of large for gestational age (LGA) (aOR = 1.20 (1.01, 1.42), 1.46 (1.07, 1.98), respectively). Grade C ICM blastocyst transfer was associated with an increased risk of macrosomia (aOR = 1.66 (1.14, 2.42)).Grade B TE and grade C TE blastocyst transfer had a lower risk of gestational diabetes mellitus (GDM) (aOR = 0.76 (0.60, 0.98), 0.69 (0.50, 0.94), respectively) than grade A TE blastocyst transfer. Limitations, reasons for caution The main limitations of this study were its retrospective nature and the relative subjectivity of blastocyst scoring. The follow-up was conducted through a phone call and some patients might not report their obstetrical and neonatal outcomes, leading to a relatively lower rate of several obstetrical outcomes. Wider implications of the findings: Transfer of a poor quality blastocyst is associated with a higher rate of C-section. The association between ICM grading and LGA and macrosomia would suggest that blastocysts with grade A ICM grading should be transferred preferentially and supports the use of current morphological grading systems for embryo prioritisation. Trial registration number N/A