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Poster Session 4

Category: Ultrasound/Imaging

Poster Session 4

(1254) Routine Third-Trimester Ultrasonography in Low-Risk Pregnancies: Examining Detection of Abnormalities in a High-Risk Population

Thursday, February 12, 2026

3:30 PM - 5:00 PM

Submitting Author(s)

ZR

Zeeraq Rana, MD

Riverside University Health System
Moreno Valley, California, United States

Coauthor(s)

BD

Brianna Dawson

University of California Riverside School of Medicine
Riverside, California, United States
RU

Ryan Uchimura, DO

Riverside University Health System
Moreno Valley, California, United States

Presenting Author(s)

Sarah D. Smithson, DO

Riverside University Health System
Moreno Valley, California, United States

Objective:
Current guidelines from the American College of Obstetricians and Gynecologists (ACOG) recommend monitoring fetal growth and amniotic fluid status in low-risk pregnancies through serial fundal height measurements beginning at 24 weeks gestation. Ultrasound is not routinely performed after the second-trimester anatomy scan unless a discrepancy in fundal height raises clinical concern. This study aims to evaluate the utility of implementing routine third-trimester ultrasounds in low-risk pregnancies as a strategy to improve detection of fetal abnormalities and potentially enhance perinatal outcomes in an underserved, high-risk population.

Study Design:
At our MFM clinic, universal 3^rd trimester ultrasounds were implemented for all patients in 2022. A retrospective study was performed of all singleton pregnancies in the study period that underwent a 2^nd trimester anatomy ultrasound and a 3^rd trimester repeat between 28-32 weeks gestation. Patients were excluded if a 3^rd trimester ultrasound or serial growth scans would have been indicated due to maternal risk factors, fetal risk factors, abnormalities on 2^nd trimester ultrasound, etc. The remaining routine 3^rd trimester ultrasounds were reviewed for clinically significant abnormalities.

Results:
Of 743 routine 3^rd trimester ultrasounds, 123 (16.6%) revealed new relevant findings. The most frequent findings were large abdominal circumference with normal estimated fetal weight (31.7%), macrosomia (27.6%), and intrauterine growth restriction (22.8%). Other detected anomalies included cardiac (4.9%), umbilical/placental (6.5%), cranial (2.4%), amniotic fluid (2.4%), extremity (1.6%), and intra-abdominal (1.6%).

Conclusion:
Routine 3^rd trimester ultrasounds in low-risk pregnancies detected clinically significant abnormalities in over 1 in 6 patients. Early detection of fetal growth and structural anomalies in this underserved population may inform care decisions and improve outcomes. These findings add to the growing body of evidence that supports the clinical value of integrating routine 3^rd trimester scans in settings with a high risk patient population.