Supplementary Material for: Fetal dilated jugular lymphatic sacs on first trimester ultrasound and their implications in antenatal screening

Objective: To investigate clinical significance, rate of genetic anomalies and fetal malformations in fetuses with dilated jugular lymphatic sacs (JLS) in the first trimester, overall and according to nuchal translucency (NT) thickness.
Methods: Retrospective multicenter cohort study of fetuses with dilated JLS at the first trimester scan. NT thickness, genetic evaluation, and fetal malformation data were collected. Logistic regression analysis was performed to evaluate impact of NT measurement on adverse outcomes.
Results: Eighty-four fetuses were included. Dilated JLS was associated with an increased NT in 75 (89.3%) fetuses; fetal structural malformations in 38 (45.2%) and genetic anomalies in 49 (64.5%). NT measurement remains the strongest predictor of genetic or structural abnormalities (OR 1.567, 95% CI 1.226 to 2.124; p = 0.001). Significantly fewer live births observed in the group with NT >99th percentile (p<0.001). Among cases with isolated JLS, a normal postnatal outcome was reported in 6 (66.7%).
Conclusions: First trimester dilated JLS are highly associated with genetic disorders and/or fetal malformations, but an increased NT remains the most important predictive factor. In cases with normal NT, dilated JLS is mostly a transient finding but approximately one-third of cases are at increased risk of adverse outcomes.