Vasa Previa. This is a dangerous condition in pregnancy where the implantation of the umbilical cord is in the membranes of the placenta rather than in the placenta itself.Therefore if the membranes rupture as they do with the onset of labor, the rupture may occur at the site of the cord implantation and rupture the vessels feeding oxygen and blood flow to the fetus prior to its birth!fortunately its rare.
Dire complication. When the umbilical cord vessels are attached to the amniotic membranes right over the internal cervical os, vasa previa is present. If undiagnosed, about half of affected fetuses die from exsanguination in labor; if diagnosed prenatally, all fetuses should survive by timely (34-35 weeks) prelabor cesarean section to avoid vessel injury in labor.
Veins unsupported. Vasa previa is an uncommon pregnancy complication where the vessels of the umbilical cord traverse across the fetal membranes before inserting into the placenta. If this traverses over the cervix, they can be torn during labor and cause the baby to lose large amounts of blood. Very difficult to diagnose prenatally.