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Recording available 2/16-5/2

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Poster Session 3

Category: Ultrasound/Imaging

Poster Session 3

(776) Chitty abdominal circumference reference better predicts large for gestational age than Hadlock AC reference

Thursday, February 12, 2026

10:30 AM - 12:00 PM

Submitting Author and Presenting Author(s)

Emily Heideman, MD

Resident Physician
University of South Florida
Tampa, Florida, United States

Coauthor(s)

RN

Rebecca Nunge, MD

Resident Physician
University of South Florida
Tampa, Florida, United States
AJ

Angela J. Johnson, MD

Resident Physician
University of South Florida
Tampa, Florida, United States
Katherine Pressman, MD

Department of Obstetrics and Gynecology, University of South Florida, Tampa, Florida
Tampa, Florida, United States
AO

Anthony O. Odibo, MD, MSCE

University of Missouri Kansas City
Kansas City, Missouri, United States
Jose R. Duncan, MD (he/him/his)

Associate Professor
University of South Florida
Tampa, Florida, United States

Objective:
To identify the fetal abdominal circumference reference that best predicts large for gestational age (LGA) neonates.

Study Design:

This was a secondary analysis of a prospective cohort including singleton pregnancies that underwent fetal growth assessment between 26 and 36 weeks’ gestation. Exclusion criteria were fetuses with chromosomal or structural anomalies and cases without delivery data. Fetal biometry measurements were compared to the Chitty abdominal circumference (AC), Hadlock AC, and Hadlock estimated fetal weight (EFW) reference charts. Predictive ability for LGA was assessed by comparing the area under the receiver operating characteristic curve (AUC). Optimal cutoffs were determined using the Youden's index of the AUC coordinates.

Results:

A total of 1,054 neonates were included, of whom 111 (10.5%) were classified as LGA. The Chitty AC reference demonstrated superior predictive performance compared to the Hadlock AC reference (AUC 0.901 [95% CI 0.873–0.929] vs. 0.896 [95% CI 0.868–0.925], p=0.045). The Hadlock EFW reference had an AUC of 0.906 [95% CI 0.878–0.933], which was not statistically different from the Chitty AC (p=0.622) or Hadlock AC (p=0.342) references. The optimal cutoffs were 0.895 for Chitty AC, 0.7450 for Hadlock AC, and 0.6575 for Hadlock EFW.

Conclusion:
The Chitty AC reference may be a more effective predictor of LGA than the Hadlock AC reference. The Hadlock EFW reference does not significantly improve prediction of LGA compared to AC measurements alone. These findings support consideration of the Chitty AC reference when assessing risk for LGA in clinical practice.