Ultrasonographic Fetal Weight Estimation: Should Macrosomia-Specific Formulas Be Utilized?
OBJECTIVE
This study aims to derive an estimated fetal weight (EFW) formula in macrosomic fetuses, compare its accuracy to the 1986 Hadlock IV formula, and assess whether including maternal diabetes (MDM) improves estimation.


METHODS
Retrospective review of nonanomalous live-born singletons with birth weight (BWT) ≥ 4 kg and biometry within 14 days of birth. Formula accuracy included: (1) mean error (ME = EFW - BWT), (2) absolute mean error (AME = absolute value of [1]), and (3) mean percent error (MPE, [1]/BWT × 100%). Using loge BWT as the dependent variable, multivariable linear regression produced a macrosomic-specific formula in a "training" dataset which was verified by "validation" data. Formulas specific for MDM were also developed.


RESULTS
Out of the 403 pregnancies, birth gestational age was 39.5 ± 1.4 weeks, and median BWT was 4,240 g. The macrosomic formula from the training data (n = 201) had associated ME = 54 ± 284 g, AME = 234 ± 167 g, and MPE = 1.6 ± 6.2%; evaluation in the validation dataset (n = 202) showed similar errors. The Hadlock formula had associated ME = -369 ± 422 g, AME = 451 ± 332 g, MPE = -8.3 ± 9.3% (all p < 0.0001). Diabetes-specific formula errors were similar to the macrosomic formula errors (all p = NS).


CONCLUSIONS
With BWT ≥ 4 kg, the macrosomic formula was significantly more accurate than Hadlock IV, which systematically underestimates fetal/BWT. Diabetes-specific formulas did not improve accuracy. A specific formula should be considered when macrosomia is suspected.
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Missouri, Kansas City, Missouri.
Blake
B
Porter
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama.
Cherry
C
Neely
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama.
Jeff
J
Szychowski
Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama.
John
J
Owen
D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D016640:Diabetes, Gestational / Q000000981:diagnostic imaging*; D005260:Female; D005320:Fetal Macrosomia / Q000000981:diagnostic imaging*; D020567:Fetal Weight; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D015999:Multivariate Analysis; D011247:Pregnancy; D011254:Pregnancy in Diabetics / Q000000981:diagnostic imaging*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal / Q000379:methods*