<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>A serious condition in which blood vessels of the umbilical cord or the placenta cross the entrance to the birth canal, beneath the fetus; this can lead to rapid fetal blood loss during labor and delivery if the blood vessels tear as the cervix dilates and the membranes rupture.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>