First-trimester and combined first- and second-trimester prediction of small-for-gestational age and late fetal growth restriction

Objective: To develop a first-trimester or combined first- and second-trimester screening algorithm for the prediction of small-for-gestational age (SGA) and late fetal growth restriction (FGR).

Methods: This was a retrospective study of women with singleton pregnancy, who underwent routine first-, second- and third-trimester ultrasound assessment. Late FGR was defined, at ≥ 32 weeks' gestation in the absence of congenital anomalies, as either (i) estimated fetal weight (EFW) or birth weight (BW) < 3^rd centile, or (ii) EFW < 10^th centile and either uterine artery mean pulsatility index (UtA-PI) > 95^th centile or cerebroplacental ratio (CPR) < 5^th centile. Neonates with BW < 10^th centile, regardless of prenatal parameters, were defined as SGA. The predictive effectiveness of maternal and first- and second-trimester factors was tested using logistic regression and receiver-operating characteristics curve analyses.

Results: A total of 3520 fetuses were included (late FGR, n = 109 (3.1%); SGA, n = 292 (8.3%)). Of the late FGR cases, 56 (1.6%) fulfilled the antenatal criteria (EFW < 3^rd centile or EFW < 10^th centile plus abnormal UtA-PI or CPR) and were defined as prenatally detected late FGR. A first-trimester screening model (comprising conception method, smoking status, maternal height, pregnancy-associated plasma protein-A (PAPP-A) and UtA-PI) could predict 50.0% of the prenatally diagnosed and 36.7% of the overall late FGR fetuses for a 10% false-positive rate (FPR). A model combining first- and second-trimester screening parameters (conception method, smoking status, PAPP-A, second- trimester EFW, head circumference/abdominal circumference ratio and UtA-PI) could predict 78.6% of the prenatally detected, and 59.6% of the overall late FGR fetuses, for a 10% FPR (area under the curve 0.901 (95% CI, 0.856-0.947) and 0.855 (95% CI, 0.818-0.891), respectively). The prediction of SGA was suboptimal for both first-trimester and combined screening.

Conclusions: A simple model combining maternal and first- and second-trimester predictors can detect 60% of fetuses that will develop late FGR, and 79% of those fetuses that will be classified prenatally as late FGR, for a 10% FPR. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.