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Poster Session 4

Category: Ultrasound/Imaging

Poster Session 4

(1179) Revisiting Nuchal Translucency Thresholds for Predicting Fetal Anomalies in Low Risk Cell-Free DNA

Thursday, February 12, 2026

3:30 PM - 5:00 PM

Submitting Author and Presenting Author(s)

Melissa E. Chambers, MD

Fellow
Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States

Coauthor(s)

LT

Luis Torres, MS

Genetic Counselor
Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States
AM

Aparna Murali, MA, MS

Genetic Counselor, Division of Clinical Genetics, Department of Human Genetics
Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States
AS

Alexandra Shambayte Lopez, BS

Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States
LK

Lorna Kwan, BS, MPH

Principal Statistician
Department of Urology, David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States
Thalia Mok, MD

Assistant Professor
David Geffen School of Medicine at University of California, Los Angeles (UCLA)
Los Angeles, California, United States

Objective:
Nuchal translucency (NT) is a well-established ultrasound marker for aneuploidy. Since implementation of cell-free DNA (cfDNA), use of the NT measurement has decreased. This study aims to investigate the role of NT in a low risk cfDNA cohort for prediction of fetal outcomes.

Study Design:
Retrospective cohort study of pregnancies with NT measurement 3 mm or greater between 11 to 14 weeks gestation and a low risk cfDNA result from January 2012 to June 2024. Primary outcome was development of a composite major abnormal ultrasound (US). Secondary outcomes included abnormal diagnostic testing and composite abnormal soft US marker. Univariate analysis was performed using Chi-square or Fisher-exact to assess outcomes by NT measurements. Multivariate logistic regression calculated adjusted odds ratios (aOR). Area under the curve (AUC) from receiver operating characteristic (ROC) curves were compared to assess the optimal cutoff for NT to predict a major abnormal US.

Results:
211 pregnancies had a low risk cfDNA but an increased NT 3 mm or greater. 30 (14.2%) had a composite major abnormal US and 11 (5.2%) had a composite abnormal soft US marker. Diagnostic testing was performed in 82 (40.0%) patients, and abnormal diagnostic testing results were found in 12 (14.8%). The median NT measurement for abnormal US was greater than normal US (3.9 mm, (IQR 3.5, 6.4) vs 3.3 mm (IQR 3.1, 3.6); p< 0.01). Increased NT was associated with significantly higher rates of composite abnormal US (p< 0.01). NT of > 4.5 mm compared to 3.0-3.4 mm had a significantly increased risk of fetal anomalies (aOR 32.5, 95% CI 8.7-121.4). NT threshold of 3.3-3.8 mm and 4.5 mm had significantly higher AUC than 3.1 mm on ROC curves (Figure 1).

Conclusion:
Only 14% of pregnancies with low risk cfDNA and increased NT had a composite abnormal US, but higher NT measurement was associated with a significantly increased risk of abnormal US. The first trimester ultrasound and NT remain valuable components of prenatal screening, but a higher threshold for increased NT measurement may be considered when evaluating risk of fetal anomalies.