Fetal Abdominal Adiposity Score and the Prediction of Large for Gestational Age Infants

To evaluate a novel ultrasound-based metric, the Fetal Abdominal Adiposity Score (FAAS), in comparison to standard fetal biometry measurements (estimated fetal weight [EFW] and abdominal circumference [AC] percentiles) for prediction of large for gestational age (LGA) newborns in patients with diabetes (DM) in pregnancy. Patients with gestational (GDM) or preexisting DM who underwent delivery of a live singleton non-anomalous fetus at a single tertiary care center between 2002 and 2013 were identified within a large, NIH-funded database of detailed pregnancy and delivery information extracted by trained research nurses. The FAAS was calculated as the biparietal diameter (BPD) minus fetal abdominal diameter (abdominal circumference/pi), normed to the gestational week for the last ultrasound prior to delivery for each patient. LGA was defined as a birth weight of ≥90th percentile for gestational age. The primary outcome was the ability of the calculated FAAS to predict LGA compared to EFW percentile and AC percentile. Predictive characteristics and the area under the receiver operating characteristic curve (AUC) were compared. Of the 1,051 eligible pregnancies evaluated, 192 (18.6%) resulted in an LGA newborn. The AUC was higher for EFW percentile (AUC 0.79 [95% CI 0.76-0.83]) vs the FAAS (AUC 0.65 [95% CI 0.60-0.69]) for prediction of LGA (p< 0.001) (Figure 1). Among 592 pregnancies for whom AC percentile was available, the AUC was highest for EFW percentile (AUC 0.80 [95% CI 0.76-0.84]) followed by AC percentile (AUC 0.75, [95% CI 0.70-0.79]), then FAAS (AUC 0.66 [95% CI 0.60-0.71]) for prediction of LGA (p< 0.001). Among pregnancies complicated by diabetes, the FAAS was less predictive of LGA infants compared with EFW percentile or AC percentile alone on third trimester ultrasound.