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Poster Session 1

Category: Ultrasound/Imaging

Poster Session 1

(164) Fetal Weight Estimation in Gastroschisis: A Formula Comparison

Wednesday, February 11, 2026

10:30 AM - 12:00 PM

Submitting Author and Presenting Author(s)

Christina Cortes, MD

Resident
University of Texas - Houston
Houston, Texas, United States

Coauthor(s)

Sami Backley, MD

Clinical Fellow PGY 9
Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Anthony Chartier, MD (he/him/his)

Resident
Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Felicia V. LeMoine, MD (she/her/hers)

Fetal Intervention Fellow
Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
AS

Ashley Salazar, DNP

UTHealth Houston Fetal Institute; Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Ramesha Papanna, MD, MPH

Professor
University of Texas Health Science Center in Houston, McGovern Medical School
Houston, Texas, United States
Jimmy Espinoza, MD, MSc

Professor
UTHealth Houston Fetal Institute; Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Anthony Johnson, DO

Professor
UTHealth Houston Fetal Institute; Division of Fetal Intervention, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States
Edgar A. Hernandez-Andrade, MD, PhD (he/him/his)

Professor
Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology and Reproductive Sciences, McGovern Medical School at UTHealth Houston
Houston, Texas, United States

Objective:
Estimating fetal weight in fetuses with gastroschisis is challenging due to altered abdominal circumference (AC) resulting from the abdominal wall defect. The Hadlock formula is widely used for estimating fetal weight (EFW) but may be less accurate in this population. The Siemer formula has been proposed as an alternative, aiming to improve EFW accuracy and growth classification. This study compared the accuracy of the Hadlock and Siemer formulas in predicting actual birthweight (BW) when ultrasound was performed within two weeks of delivery.

Study Design:
Fetuses with gastroschisis who underwent EFW assessment within two weeks of delivery were retrospectively analyzed at a single tertiary referral center between 2016-2024. EFW was calculated using the same biometric parameters for both formulas. Actual BW was recorded, and the absolute percent difference between EFW and BW was calculated. The formula with the smaller absolute difference from BW was considered more accurate.

Results:
A total of 45 fetuses were included. The median gestational age at the last ultrasound was 34w1d (29+6 to 36+6), and the median BW was 2,340 g (1,360–3,210 g). The Siemer formula was closer to the actual BW in 26 cases (57.8%), while the Hadlock formula was more accurate in 19 cases (42.2%), though this difference was not statistically significant (p = 0.2). The mean interval between ultrasound and delivery was 0.9 weeks. Among fetuses delivered within one week of ultrasound, the mean percent difference between Hadlock EFW and BW was -15.8% (SD 7.9%), compared to -14.1% (SD 10.2%) for Siemer. For those delivered 1–2 weeks later, mean differences were +20.8% (SD 11.4%) for Hadlock and +21.5% (SD 11.3%) for Siemer.

Conclusion:
In fetuses with gastroschisis, no significant difference in accuracy was found between the Hadlock and Siemer formulas. However, EFW predictions were more accurate when delivery occurred within one week of ultrasound.