Foetal blood loss in abnormal cord insertion is seen in (AIIMS Nov2010)
Vasa praevia - usually associated with a minor degree of placenta praevia, so the vessels that run in the membranes may cross the os uteri in front of the presenting part and may be torn when the membranes are ruptured (spontaneous or artificial) or may rupture during labour and present as APH, if the condition is not recognized and promptly treated, the fetus may get severely exsanguinated.
a. Battledore or Marginal placenta - Generally the umbilical cord is inserted at or near the centre of the placenta, If it is inserted at the margin of the placenta
b. Placenta succenturiate - succenturiate lobe which is an accessory lobe at some distance from the main placental mass, and connected to it by membranes containing branches of the umbilical vessels
c. The decidua basales becomes the maternal portion of the placenta