Vasa Previa

Vasa Previa During Pregnancy

The definition of this extremely rare, yet devastating condition is as follows: fetal vessels crossing or running in close proximity to the inner cervical os. These vessels course within the membranes (unsupported by the umbilical cord or placental tissue) and are at risk of rupture when the supporting membranes rupture. It carries a high mortality rate of 50-100% of cases ending in death of the fetus.

This condition takes place when the vessels of the cord grow on its exterior instead of its interior, which usually results in death for the fetus unless an emergency caesarean section is performed. As blood vessels run through the umbilical cord, then grow out of the cord and into the placenta, vasa previa occurs. Without the toughness of the fibrous cord (strength is provided when vessels grow on the inside of the umbilical cord), the blood vessels have very little support from the fetal membranes (bags of water). When labor occurs and a woman’s water breaks, the unsupported vessels in and around the umbilical cord tear, resulting in death of the baby from blood loss within 2-3 minutes.

Causes of Vasa Previa

There haven’t been many studies conducted in the past of vasa previa, due to its rarity. However, experts believe that a possibility could be that the nutrients in the bottom of the placenta are not as rich as the ones in the top of the placenta. As a plant would grow towards the sun, experts think the vessels grow toward the better nutrition. Unfortunately, no one really knows what causes vasa previa, however there are characteristics that many cases share, such as:

  • Women with low-lying placentas
  • Multiple pregnancies
  • Pregnancies where IVF was used
  • Women with placentas that consist of more than one piece

Vasa Previa Symptoms

Unfortunately, in some cases, there are absolutely no symptoms or signs to warn of vasa previa. It isn’t until labor when the fetus is at risk, or it’s too late after a stillbirth delivery that doctors and health care professionals diagnose vasa previa. Something expectant mothers should watch for, especially in their second and third trimesters, is the sudden onset of painless vaginal bleeding. The lack of pain is usually a signal that vasa previa is present.

Vasa previa can be present if any of the following conditions exist:

  • Velamentous cord insertion
  • Bi-lobed placenta
  • Succenturiate-lobed placenta
  • Low-lying placenta or placenta previa
  • Multiple pregnancies
  • Pregnancies resulting from IVF
  • Maternal history
  • Uterine surgery

Vasa Previa Treatment

If you are lucky enough to catch vasa previa early on, chances of survival rates range from 50-95%. The condition can be detected through the use of transvaginal sonography, mostly combined with color Doppler. If you feel you have any of the warning signs listed above, you should have this test done to rule out vasa previa. Once diagnosis is made, the next steps depend on how far along the pregnancy term is. Doctor’s will perform a c-section as the method of delivery, however, they don’t want to perform the c-section if it’s too early and problems can arise from the premature birth. Experts in the field suggest hospitalization in the third trimester, delivery by 35 weeks, and an immediate blood transfusion to the baby in the event of a rupture. Steroids are sometimes used to mature a baby’s lungs.

[Page updated April 2010]