Am J Perinatol 2015; 32(10): 968-972
DOI: 10.1055/s-0035-1545664
Original Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Ultrasonographic Fetal Weight Estimation: Should Macrosomia-Specific Formulas Be Utilized?

Blake Porter
1   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Missouri, Kansas City, Missouri
,
Cherry Neely
2   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama
,
Jeff Szychowski
2   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama
3   Department of Biostatistics, University of Alabama at Birmingham, Alabama
,
John Owen
2   Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Alabama at Birmingham, Alabama
› Author Affiliations
Further Information

Publication History

07 August 2014

08 January 2015

Publication Date:
02 March 2015 (online)

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Abstract

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.

Study Design 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.

Note

This research was presented in abstract form at the 34th Annual Meeting of the Society of Maternal-Fetal Medicine; February 2014; New Orleans, LA.