Definition:
A complication in the formation of the umbilical cord that can lead to serious pregnancy complications, such as vasa previa.
In a normal gestational sac, the umbilical cord is inserted into the middle of the placenta and entirely enclosed in the amniotic sac. Velamentous insertion means that the cord is inserted on the amniotic membrane rather than on the placenta with blood vessels stretching along the membrane between the insertion point and the placenta.
Velamentous insertion occurs in 1.1% of singleton pregnancies and 8.7% of twin pregnancies.
Source
International Vasa Previa Foundation, "Velamentous Insertion of the Umbilical Cord." Accessed 29 Jun 2008.
