EP08.21: Prediction of adverse intrapartum outcomes at 35–37 weeks

Large-for-gestational age (LGA) and small-for-gestational-age (SGA) neonates increase the risk of emergency operative delivery (EOD) and adverse maternal outcomes (AMO). Identifying women at 35-37 weeks at increased risk of these events offers a window of opportunity to mitigate these outcomes. This study evaluated the performance of biometric and Doppler parameters assessed at a routine third trimester scan, in combination with maternal characteristics, in predicting adverse intrapartum outcomes. This was a cohort study of low-risk singleton pregnancies undergoing routine ultrasound at 35+0 - 37+6 weeks. Demographic characteristics, estimated fetal weight (EFW), abdominal circumference (AC) centiles, and the Pulsatility Index (PI) of the Umbilical Artery (UA), Middle Cerebral Artery (MCA), and Uterine Artery (UtA) were evaluated. The Cerebroplacental ratio (CPR) was calculated and all indices were converted to Multiples of the Median (MoM). Multivariable logistic regression analysis was performed. Receiver-operating curves (ROC) were created to determine factors predictive of EOD (emergency Caesarean, forceps or vacuum delivery) and AMO (High Dependency Unit admission, >1000ml blood loss or EOD). A total of 14,161 pregnancies were included. After adjustment for confounders, EFW centile (adjusted odds ratio (aOR) 1.01, 95% CI, 1.0-1.02, p < 0.0001) and UA PI (aOR 3.6, 95% CI, 1.1-11.5, p = 0.03) were independent predictors of EOD. EFW centile (aOR) 1.01, 95% CI, 1.0-1.01, p < 0.0001), UA PI (aOR 4.1, 95% CI, 1.4-12.4, p < 0.0001) and CPR (aOR 2.8, 95% CI, 1.1-7.1, p < 0.001) were independent predictors of AMO. The combination of maternal demographic characteristics and EFW centile, UA, MCA and UtPI and CPR was associated with an Area under the Curve (AUC) of 0.74 (95% CI 0.73-0.75) p < 0.001 for the prediction of EOD and 0.71 (95% CI 0.7-0.72 p < 0.001) for the prediction of AMO. In an unselected population, the combination of maternal demographic characteristics and sonographic variables can predict adverse intrapartum events and adverse maternal outcomes.