Prediction of large for gestational age by various sonographic fetal weight estimation formulas—which should we use?

Objective:as sonographic estimation of fetal weight (efw) carries substantial impact, especially in large-for-gestational-age (lga) neonates, we aimed to compare the accuracy of various formulas for prediction of lga neonates.study design:retrospective cohort study of singleton gestations at term, with efw up to 7 days before delivery (2007 to 2014). small-for-gestational-age neonates were excluded. lga prediction for various formulas was evaluated by: (i) measures of performance (sensitivity, specificity, etc.); (ii) systematic and random errors (se and re) and the proportion of estimates (poes) exceeding 10% of actual birth weight. best performing formula was defined as the one with the lowest euclidean distance [=square root of (se2+re2)].results:out of 62 102 deliveries, 7996 met inclusion criteria, of which 1618 neonates were lga (22%). there was a considerable variation in sensitivity (74.6±16.3%, 23.5% to 99%), specificity (86.3±10.6%, 51.7% to 99.6%), positive predictive value (64.9±12.4%, 35.6% to 93.8%), positive likelihood ratio (lr; 9.3±10.9, 2.1 to 54.2) and negative lr (0.3±0.16, 0.02 to 0.8), a mild variation in the negative predictive value (92.9±3.7%, 82.3% to 99.5%) and a minimal variation in the area under the curve (94.3%, 93.0 to 95.1; mean±s.d., range for all). absolute se was higher for the lga group in 11/20 formulas (55%). the re and poe were lower in 19/20 (95%) and 14/20 (70%) for the lga neonates, respectively.conclusion:there is a wide variation in efw formulas performance for detecting lga. hadlock’s formula (1985) combining abdominal circumference, femur length and biparietal diameter ranked highest.