Care and treatments for vasa previa
Vasa previa is when unprotected blood vessels implanted in the membranes or sac run from the placenta across the inside of the woman's cervix. This variation occurs when the placenta grows in an unusual way, either as a succenturiate or bi-polar formation or as a velamentous insertion of the cord. Vasa previa is very rare, thought to occur for about 1 in 2000 - 3000 pregnancies (0.0005 - 0.0003%).
Succenturiate formation is when the placenta has a satellite lobe that implants away from the main body of the placenta, but is connected to the placenta by a large blood vessel (or several vessels) implanted in the amniotic sac or membrane. A bi-polar or bipartite placenta is where the placenta grows as two equal-sized lobes, joined by a blood vessel (or more than one blood vessel).
Image 4-46 shows a placenta with a succenturiate lobe and the blood vessel trailing through the sac or membrane.
A velamentous insertion is where the cord implants in the membrane of the amniotic sac instead of the placenta. Large blood vessels run though the membrane to the placenta. This occurs in about 1% of singleton pregnancies and up to 7% of twin pregnancies.
Image 4-47 shows a placenta with a velamentous Insertion.
We don't know exactly why vasa previa forms, but it is often associated with a
low-lying placenta or a previous caesarean birth, women who smoke, multiple pregnancies and assisted conceptions, such as IVF.
NOTE: These two types of placenta formations do not necessarily mean there is definitely vasa previa, especially if the placenta is implanted high in the uterus, away from the cervix. If there is no vasa previa, then the pregnancy and birth can generally progress normally.
Care and treatments for vasa previa