Prediction of Small for Gestational Age: Accuracy of Different Sonographic Fetal Weight Estimation Formulas

Abstract

Objective: To compare the accuracy of various sonographic estimated fetal weight (sEFW) formulas for the prediction of small for gestational age (SGA) neonates. Methods: A retrospective analysis of 6,126 fetal biometrical measurements performed within 3 days of delivery. SGA prediction was evaluated for various sEFW formulas by calculating the sensitivity, specificity, positive/negative predictive value (PPV/NPV), likelihood ratio (+LR/-LR), overall accuracy and area under the receiver operating characteristic curve (AUC). Systematic error, random error, proportion of estimates >10% of birth weights, actual and absolute weight differences were compared between SGA and non-SGA neonates. Results: Overall, 638 (10.4%) neonates were SGA. There was considerable variation among formulas in sensitivity (mean ± SD, 62 ± 14.4%; range, 32.4-91.2), PPV (72.5 ± 10.7%; 45.8-95.6) and +LR (24.2 ± 10.9; 7.2-57.3), mild variation in specificity (96.6 ± 2.7%; 87.4-99.4), NPV (94.6 ± 5.3%; 72.2-98.9) and -LR (0.4 ± 0.1; 0.1-0.7) and minimal variation in AUC (mean, 0.93; range, 0.91-0.93). The majority of formulas had a lower accuracy for the SGA neonates, with systematic error and random error ranging from -4.2 to 14.3% and from 8.4 to 12.9% for SGA, and from -8.7 to 16.1% and from 7.2 to 10.5% for non-SGA, respectively. Conclusion: sEFW formulas differ in their accuracy for SGA prediction. In our population, the most accurate formula for SGA prediction was Hadlock's formula utilizing femur length, abdominal and head circumference.

Ultrasonographic estimation of fetal weight: development of new model and assessment of performance of previous models

“…In general, previous studies assessing the accuracy of different models for EFW in the prediction of birth weight have reached the conclusion that either the most, or among the most, accurate models were those reported by Hadlock et al . in all pregnancies, including those with a small or large baby.…”

“…Studies describing new models have often reported that their model was superior to previously published ones, but this is an inevitable consequence of deriving and testing a model in the same population. In general, previous studies assessing the accuracy of different models for EFW in the prediction of birth weight have reached the conclusion that either the most, or among the most, accurate models were those reported by Hadlock et al 15 in all pregnancies, including those with a small or large baby [50][51][52][53][54][55][56][57] .…”

Comparison between Three Methods of Fetal Weight Estimation during the Active Stage of Labor Performed by Residents: A Prospective Cohort Study

“…This finding is consistent with the pathophysiology of the development of placental insufficiency that mostly occurs in the third trimester, thus a previous growth scan could not possibly predict SGA at term. A recent study by Gabbay-Benziv et al [25] on a large cohort of nonlaboring women demonstrated that the formula of Hadlock et al [14] combining FL, AC, and HC performed best for the detection of SGA. In the current study, the Hadlock formula that performed best for SGA detection combined FL, BPD, AC, and HC.…”

Acardiac twin pregnancies part II: Fetal risk of chorangioma and sacrococcygeal teratoma predicted by pump/acardiac umbilical vein diameters

“…The systematic and random error in these methods is estimated to be from ‐8.7 to 16.1% and from 7.2 to 10.5% in a recent evaluation (Gabbay‐Benziv et al, ), with the most accurate method confirmed to be Hadlock's formula (Hadlock et al, ), which calculates estimated fetal weight from three biometric measurements: head and abdominal circumference and femoral length. These limitations are even more apparent when cardiac output is estimated in complex situations such as in an SCT that may be the size of the fetus.…”