Differential performance of first‐trimester screening in predicting small‐for‐gestational‐age neonate or fetal growth restriction

Abstract

ABSTRACT Objective To assess the ability of integrated first‐trimester screening, combining maternal characteristics and biophysical and biochemical markers, to predict delivery of a small‐for‐gestational‐age (SGA) neonate, and compare this with its ability to predict fetal growth restriction (FGR). Methods This was a prospective cohort study of singleton pregnancies undergoing routine first‐trimester screening. SGA was defined as birth weight (BW) < 10 th percentile and FGR was defined as an ultrasound estimated fetal weight < 10 th percentile plus Doppler abnormalities, or BW < 3 rd percentile. Logistic regression‐based predictive models were developed for predicting SGA and FGR. Models incorporated the a‐priori risk from maternal characteristics, and mean arterial pressure, uterine artery Doppler, placental growth factor and soluble fms‐like tyrosine kinase‐1. Results In total, 9150 births were included. Of these, 979 (10.7%) qualified for a postnatal diagnosis of SGA and 462 (5.0%) for a prenatal diagnosis of FGR. For predicting SGA, the model achieved a detection rate of 35% for a false‐positive rate (FPR) of 5% and 42% for a 10% FPR. The model's performance was significantly higher for predicting FGR ( P < 0.001), with detection rates of 59% and 67%, for a FPR of 5% and 10%, respectively. Conclusion The predictive performance of first‐trimester screening for cases with growth impairment by a combination of maternal characteristics and biophysical and biochemical markers is improved significantly when a prenatal and strict definition of FGR is used rather than a postnatal definition based on BW. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.