Serial Ultrasound and Monitoring for Velamentous Cord Insertion

Initial Detection and Assessment

The American College of Radiology recommends systematic evaluation of velamentous cord insertion (VCI) at the routine second-trimester anatomy scan (18-22 weeks) using transabdominal ultrasound with color Doppler, as VCI is associated with adverse pregnancy outcomes 1, 2
Color Doppler ultrasound has 67% sensitivity and 100% specificity for detecting VCI in the second trimester, and when VCI is identified, transvaginal ultrasound with color Doppler is superior for detecting concurrent vasa previa 3

The American College of Radiology guidelines recommend serial surveillance for the remainder of pregnancy, focusing on fetal growth, amniotic fluid assessment, and umbilical artery Doppler velocimetry, once VCI is diagnosed 1, 2
Umbilical artery Doppler assessment should be performed when growth restriction is suspected or documented, as part of the surveillance protocol 1, 2

VCI occurs in up to 22% of monochorionic twins and requires even more intensive surveillance, with fetal biometry every 2-3 weeks starting at 16 weeks 1, 2, 6
The presence of VCI in one or both twins increases the risk of twin-twin transfusion syndrome from 7% to 27%, and further increases the risk of growth discordance with discordant cord insertion sites 4, 7

The American College of Radiology guidelines suggest that the mode of delivery depends on additional risk factors rather than VCI alone, and vaginal delivery is generally preferred for singleton pregnancies with isolated VCI without vasa previa, but cesarean delivery should be strongly considered when VCI is combined with fetal growth restriction and abnormal Doppler findings 3