EP18.16: Fetal dilated jugular lymphatic sacs on first trimester ultrasound and their implications in antenatal screening

To investigate the clinical significance and the rate of genetic anomalies and fetal malformations in fetuses with dilated jugular lymphatic sacs (JLS) at the first trimester ultrasound, overall and according to nuchal translucency (NT) thickness. Retrospective cohort study of fetuses with a first trimester diagnosis of dilated JLS from four clinical centres. Data regarding NT thickness, genetic evaluation, and fetal malformation were collected. We used logistic regression analysis to evaluate the impact of nuchal translucency measurement on the risk of a chromosomal, genetic, or structural anomaly among fetuses with a dilated JLS. Sixty-eight fetuses were included in this study. The presence of dilated JLS was associated with an increased NT in 59 (86.8%) fetuses, of which 45 (66.2%) had a NT >99th percentile and 14 (20.6%) between the 95th and the 99th percentiles. Fetal structural anomalies were found in 29 (42.6%) of cases, of which 24 (35.3%) were identified at the first trimester scan, 6 (8.8%) at the second trimester scan and 2 (2.9%) at follow-up scans. Genetic anomalies were present in 36 (52.9%), of which chromosomal anomalies were the most frequent, 35 (51.5%). Increased NT is significantly associated with genetic or structural anomalies, (OR 1.82, 95% CI 1.33 to 2.71). Significantly fewer live births were observed in the group of fetuses with NT >99th percentile (p = 0.0002), primarily due to terminations of pregnancy. Among cases with an isolated finding of JLS at the first trimester scan, a normal postnatal outcome was reported in 6 (66.7%). The presence of dilated JLS in the first trimester scan is highly associated with genetic disorders and/or fetal malformations, especially in combination with increased NT. In cases of isolated dilated JLS with NT <95th percentile, the pregnancy outcome is mostly good.