The use of ultrasound to detect small-for-gestational-age infants in patients with elevated human chorionic gonadotropin on maternal serum screening

We evaluated serial sonography for the antenatal detection of small-for-gestational-age (SGA) infants in pregnancies with elevated human chorionic gonadotropin (hCG) levels on midtrimester triple-marker screen. A retrospective cohort study was performed at Saddleback Memorial Medical Center where serial ultrasounds from 26 weeks to delivery are generally recommended for patients with hCG levels >2.0 Multiple of the Median (MoM). From 1999 to 2007, 659 subjects were identified for analysis. The incidence of intrauterine growth restriction (IUGR) and SGA were 5.2% and 7.3%, respectively. Antenatal ultrasound identified 31.3% of SGA infants. Compared with estimated fetal weight (EFW) <10th percentile alone, abdominal circumference (AC) <10th percentile improved the detection of SGA from 31.3% (95% confidence interval [CI], 18.7 to 46.3) to 35.4% (95% CI, 22.2 to 50.5). Using either EFW or AC further increased the sensitivity to 45.8% (95% CI, 31.4 to 60.8). The sensitivity for the detection of SGA was 100% when an EFW cutoff of 75% was used. Ultrasound can be used to detect SGA infants in patients with elevated hCG levels on midtrimester serum screening. A sonographic estimated fetal weight 75th percentile appears to be a safe cutoff to rule out all fetuses at risk for SGA.