What are the key clinical signs and symptoms that may indicate vasa praevia in a pregnant patient?

Key clinical signs and symptoms that may indicate vasa praevia in a pregnant patient include painless vaginal bleeding in the second or third trimester, often following rupture of membranes, and fetal distress evidenced by abnormal fetal heart rate patterns. These signs arise because fetal blood vessels traverse the membranes unprotected, making them vulnerable to rupture and causing fetal hemorrhage.

Additionally, there may be no maternal pain despite significant bleeding, which is a critical clinical clue. Ultrasound with colour Doppler is essential for diagnosis, as clinical signs alone are often insufficient to detect vasa praevia before delivery.

In summary, the hallmark clinical presentation is painless antepartum bleeding combined with signs of fetal compromise, but definitive diagnosis relies on targeted ultrasound screening, especially in women with risk factors such as low-lying placenta or velamentous cord insertion.

These points integrate UK guideline emphasis on the importance of antenatal detection and the literature highlighting the subtlety of clinical signs and the role of ultrasound in confirming diagnosis (NG201, NG192) (Donnolley et al., 2013).