Maternal and Antenatal Complications in Pregnancies Complicated by Fetal Intra-Abdominal Umbilical Vein Varix.

Background/Objectives: Prior research suggests that fetal intra-abdominal umbilical vein varix (FIUVV) is associated with an increased risk of structural anomalies, aneuploidy, and poor obstetrical outcomes such as growth restriction and demise. Data in prior studies, however, are limited. The aim of this study is to determine the natural progression of FIUVV and its association with maternal and antenatal complications. Methods: This is a retrospective cohort study of singleton pregnancies that received an ultrasound between July 2020 and June 2023. FIUVV was diagnosed based on the presence of a focal intra-abdominal vein dilation measuring >9 mm or >50% wider than the diameter of the intra-hepatic umbilical vein. Controls were matched 1:1 based on same date as the cases and by similar gestational age. Maternal and fetal outcomes were collected. Results: A total of 105 pregnancies complicated by FIUVV met inclusion criteria, and 105 controls were identified. Diagnosis was most commonly obtained at 32 gestational weeks with average dilation at 11.2 mm. Concurrent structural defects were detected in 19 (18.1%) fetuses. Compared to controls, pregnancies complicated by FIUVV had similar rates of diabetes, hypertensive disorders, COVID-19, active smoking, and abnormal genetic screening. There were also similar rates of fetal growth restriction, large-for-gestational-age fetuses, and oligohydramnios. Pregnancies complicated by FIUVV were more likely to have polyhydramnios compared to controls (p < 0.01). Conclusions: In the large cohort of FIUVV, outcomes were favorable. FIUVV was not associated with common maternal co-morbidities. Polyhydramnios was more common in pregnancy complicated by FIUVV, but fetal growth abnormalities were similar compared to controls.