Mid-pregnancy fetal biometry, uterine artery Doppler indices and maternal demographic characteristics: role in prediction of small-for-gestational-age birth

Introduction The aim of this study was to evaluate the role of mid-trimester fetal biometry, uterine artery Doppler indices and maternal demographics in prediction of small-for-gestational-age (SGA) birth. Materials and methods We conducted a retrospective cohort study in a single referral center. The study included 23 894 singleton pregnancies scanned between 19 and 24 weeks of gestation. Maternal demographics included age, body mass index and ethnicity. Fetal biometry, birthweight and uterine artery pulsatility index values were converted into centiles. Multivariable logistic regression analysis was performed and the predictive accuracy was assessed using receiver operating characteristic curve analysis. The main outcome measure was prediction of delivery of preterm and term SGA neonates defined as a birthweight in the lowest centile groups (<10th, <5th and <3rd centiles). Results Maternal ethnicity, fetal biometry and uterine artery Doppler indices were significantly associated with the risk of SGA <5th centile (p < 0.01). Maternal factors or fetal biometry alone showed poor to moderate performance in prediction of term and preterm SGA <5th centile at a 10% false-positive rate. Uterine artery pulsatility index alone was able to predict 25, 60 and 77% of SGA <5th centile delivering at >37, <37 and <32 weeks of gestation respectively at a 10% false-positive rate; maternal factors, fetal biometry and uterine artery Doppler combined detected 40, 66 and 89% of term, preterm and very preterm SGA <5th centile at a 10% false-positive rate. Conclusions Second-trimester screening can identify the majority of pregnancies at high risk of SGA birth and showed a higher performance for earlier gestational ages at birth and lower birthweight centiles.