First-Trimester Prediction Of Small-For-Gestational Age In Pregnancies At False-Positive High Or Intermediate Risk For Fetal Aneuploidy

Objectives To explore the risk of small-for-gestational age (SGA) and fetal growth restriction (FGR) and to test the performance of first-trimester screening for SGA and FGR in women with a false-positive high or intermediate risk for aneuploidy.Methods This was a prospective cohort study of women with a singleton pregnancy attending for a routine first-trimester scan. The risks of aneuploidy and preterm SGA (defined as birth weight < 10th percentile with delivery before 37 weeks) were determined according to Fetal Medicine Foundation algorithms. In non-malformed euploid pregnancies, the predictive performance of both the aneuploidy and preterm SGA risks was evaluated for SGA, FGR (defined as birth weight < 3rd centile), preterm SGA and early SGA (delivery before 34 weeks), using receiver-operating-characteristics (ROC) curve analysis, in those with a high or intermediate risk of aneuploidy and in the overall population.Results A total of 2053 pregnancies were included in the analysis, of which 191 (9.3%) were at high or intermediate risk for aneuploidy (>= 1/1000) and 304 (14.8%) were at high risk for preterm SGA (>= 1/100). In total, there were 140 (6.8%) cases of SGA, 61 (3.0%) of FGR, 44 (2.1%) of preterm SGA and 33 (1.6%) of early SGA. Among women with a false-positive high or intermediate risk for aneuploidy, the rates of SGA, FGR, preterm SGA and early SGA were 13.6% (26/191), 7.9 % (15/191), 6.8% (13/191) and 5.8% (11/191), respectively. Compared with women with a first-trimester low risk for preterm SGA, regardless of aneuploidy risk, those with a high risk for preterm SGA and a high or intermediate risk for aneuploidy had relative risks for SGA, FGR, preterm SGA and early SGA of 6 (95% CI, 3.9-9), 9.2 (95% CI, 5.1-16.5), 13.4 (95% CI, 6.9-26.1) and 17.6 (95% CI, 8.1-38.2), respectively. The predictive performance for SGA of the preterm SGA algorithm was higher in women at high or intermediate risk for aneuploidy than in the overall population (area under the ROC curve (AUC), 0.8 vs 0.7; P<0.001). Among women at high or intermediate risk for aneuploidy, the predictive performance of the preterm SGA algorithm was better than that of the aneuploidy algorithm for SGA (AUC, 0.80 vs 0.58; P=0.003), preterm SGA (AUC, 0.85 vs 0.65; P=0.013) and early SGA (AUC, 0.86 vs 0.60; P=0.002).Conclusion In women with a first-trimester false-positive high or intermediate risk of aneuploidy, further screening for SGA allows stratification of the risk for fetal growth disorders. Copyright (C) 2020 ISUOG. Published by John Wiley & Sons Ltd.