Association between blastocyst morphometrics and live birth, obstetric complications and perinatal outcomes

RESEARCH QUESTION: Are blastocyst morphometrics, specifically diameter, inner cell mass (ICM) area and trophectoderm (TE) cell count, associated with live birth, obstetric complications and perinatal outcomes? DESIGN: This retrospective single-centre cohort study involved 1132 vitrified-warmed single-blastocyst transfers performed between May 2018 and July 2024. Blastocyst diameter, ICM area and TE cell count were quantitatively measured before vitrification. The effects of blastocyst morphometric parameters on live birth, obstetric complications and perinatal outcomes were evaluated using statistical models that accounted for potential confounding factors. RESULTS: increase in ICM area and each 10-cell increase in TE cell count was associated with increased live birth rates (ICM area: marginal odds ratio [mOR] 1.023, 95% CI 1.009-1.037, P = 0.001; TE cell count: mOR 1.101, 95% CI 1.038-1.168, P = 0.001). Each 10-cell increase in TE cell count was significantly associated with increased birthweight (β = 19.47 g, 95% CI 4.91-34.02 g, P = 0.010) and placental weight (β = 8.64 g, 95% CI 3.00-14.27 g, P = 0.003), as well as with a reduced risk of low birthweight (LBW; mOR 0.860, 95% CI 0.743-0.995, P = 0.044), small for gestational age (SGA; mOR 0.693, 95% CI 0.541-0.888, P = 0.004) and hypertensive disorders of pregnancy (HDP; mOR 0.740, 95% CI 0.600-0.912, P = 0.005). CONCLUSIONS: Both ICM area and TE cell count were independently associated with live births following embryo transfer. Once pregnancy is established, TE morphology, specifically TE cell count, further influences birthweight, placental weight and incidence of LBW, SGA and HDP.