Understanding Vasa Previa: Causes, Symptoms, and Management

Written by Sarah Gleim
Medically Reviewed by Shruthi N, MD on April 27, 2025
3 min read

Vasa previa is a rare complication that can occur during pregnancy. It happens when some of the blood vessels that connect your baby's umbilical cord to your placenta cross over, or near, the opening of your cervix. 

When your water breaks, these blood vessels can rupture, too. This can cause your baby to lose a lot of blood or even die. It's important to diagnose early in your pregnancy to prevent complications during labor, usually by delivery via C-section.

There are a few causes of vasa previa:

Velamentous cord insertion 

Vasa previa can happen when your baby's umbilical cord doesn't implant into your placenta like it's supposed to. Instead, with velamentous cord insertion, the umbilical cord attaches outside of the placenta. This leaves the blood vessels inside unprotected and without the cushion of the gel-like substance called Wharton's jelly. They also have farther to go to get the nutrients from the placenta.

Bilobed placenta

Vasa previa can also happen when your placenta splits into two lobes that are about the same size. Your umbilical cord can be implanted in either lobe, velamentous, or between both.

Succenturiate placenta

A succenturiate placenta is similar to a bilobed placenta, but instead of two equal-sized lobes, one or more smaller lobes develop from the main placenta. Succenturiate placenta is rare, but it can also cause vasa previa.

Your placenta should attach to the top or side of your uterus, nowhere near your cervix (the opening of your uterus). If you have placenta previa, your placenta attaches low in your uterus, completely or partially covering your cervix. Placenta previa can cause heavy bleeding during delivery if your baby isn't delivered by C-section.

Placenta previa also increases your risk of vasa previa.

You may not have any symptoms if you have vasa previa. Some people have bleeding that's dark in color, though it's not very common.

Vasa previa can happen during any pregnancy. However, certain conditions can put some people at a higher risk of developing it, including:

Your doctor or health care provider will likely detect it during a routine exam and ultrasound, usually between weeks 18 and 26 of your pregnancy.

If they note any signs of problems, they may also do a transvaginal ultrasound for more detailed views to look for issues with the blood vessels from your umbilical cord near your cervix. They'll also look to see where your placenta is in relation to your cervical opening and if it has additional lobes.

The main treatment is to safely manage your pregnancy and to deliver with a scheduled C-section. Treatment may also include:

  • Monitoring you and your baby with regular nonstress tests
  • Hospital admission around 30 to 32 weeks to more closely monitor the baby
  • Corticosteroids to help your baby's lungs mature
  • Pelvic rest, which means avoiding sex or putting anything in your vagina
  • Planned C-section delivery between 34 and 37 weeks
  • Emergency C-section if your membranes rupture early, you have vaginal bleeding, or your baby is in distress

Can vasa previa be managed for a safe delivery?

Yes. In nearly all cases, your doctor can manage it safely so you can deliver via C-section without any complications.

What are the risks if vasa previa goes undetected?

The main risk if it goes undetected is severe blood loss for your baby before or during delivery.