Fetal blood loss occurs in
Vasa pre occurs when there is velamentous inseion of placenta i.e. the umbilical cord vessels are splitting before getting attached to the placenta. The inseion of the cord may be close to the internal os. The fetal head can compress the cord leading to rupture of vessels. In this case the blood loss occurs from fetal vessels.
Vasa pre
Placenta pre
Cord prolapse
Abruption
Antepaum Haemorrhage