In this condition, blood vessels of the afterbirth (placenta) traverse through the membranes and occupy a position below the presenting part of the baby (usually head).
There is no particular reason for this condition but identification by ultrasonography is helpful to avert a catastrophe.
In Vasa praevia, the blood comes directly from the baby and if not recognized early, the chances of the baby dying in the womb are very high. Bleeding starts as soon as the membranes rupture (breaking of waters). On gentle internal examination, pulsating vessels may be felt. The baby heart rate as recorded from the mother's tummy shows signs of distress.
Ultrasonography and Color Doppler studies can diagnose the condition. Internal examinations need to be avoided as they can lead to sudden heavy bleeding.
Prompt recognition of the condition and delivery by cesarean section is the key and gives optimal results for the baby.