What imaging techniques are recommended for the diagnosis of vasa praevia during routine antenatal care?

Imaging techniques recommended for diagnosing vasa praevia during routine antenatal care primarily involve detailed ultrasound assessment with colour Doppler. Transvaginal ultrasound combined with colour Doppler imaging is the preferred method to identify fetal vessels crossing or running near the internal cervical os, which is diagnostic of vasa praevia. This approach allows clear visualisation of the fetal vessels and their relationship to the cervix, improving diagnostic accuracy.

Routine antenatal care includes targeted ultrasound scans around 18–20 weeks gestation, during which placental location and cord insertion are assessed. If risk factors for vasa praevia are present (such as low-lying placenta, velamentous cord insertion, or multiple pregnancies), a detailed transvaginal ultrasound with colour Doppler is recommended to confirm or exclude vasa praevia.

While MRI is occasionally considered in complex placental abnormalities like placenta accreta spectrum, it is not routinely recommended for vasa praevia diagnosis during antenatal care.

Recent literature supports the use of colour Doppler ultrasound as the gold standard for prenatal diagnosis of vasa praevia, highlighting its high sensitivity and specificity, which enables planned delivery strategies to reduce perinatal mortality (Jain and Gagnon, 2023; Conyers et al., 2024).