Vasa Previa Diagnosis and Treatment to Prevent Stillbirth

This Condition May Develop Along with Placenta Previa

Pregnant woman having ultrasound scan
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In a normal, healthy pregnancy, the blood vessels running between the fetus and the placenta are contained in the umbilical cord. In an estimated one in 2,500 pregnancies, however, a serious complication called vasa previa occurs. With vasa previa, some of the blood vessels grow along the membranes in the lower part of the uterus at the cervical opening. If the condition is not detected in advance, the blood vessels can rupture during labor, causing massive blood loss for both mother and baby and potentially resulting in a stillbirth.

Studies show that 56 percent of instances of vasa previa that go undiagnosed result in perinatal mortality or stillbirth. When the condition is detected in pregnancy, however, the fetal survival rate rises to 97 percent.

Risk Factors and Causes of Vasa Previa

Normally, the blood vessels of the umbilical cord and the placenta are insulated inside the amniotic sac. In vasa previa, some of the blood vessels are present in the membranes outside of the sac and therefore don't benefit from this crucial protection.

Causes of vasa previa include:

Velamentous insertion of the umbilical cord

A velamentous insertion of the umbilical cord is a pregnancy complication in which the umbilical cord inserts itself into the amniotic membrane rather than in the placenta. The baby's blood vessels then stretch along the membrane between the insertion point and the placenta, leaving them unprotected by the amniotic sac, which normally encases the placenta as well as the umbilical cord.

A multi-lobed placenta

In rare cases, the placenta is divided into two or three "lobes" by a membrane. Vasia previa can occur when the umbilical cord inserts itself into one of these membranes.

It is not known exactly what causes a multi-lobed placenta, but genetics, advanced maternal age, diabetes, a history of chronic seizures, and cigarette smoking or excessive vomiting during pregnancy are thought to be factors.

Placenta previa

Sometimes the placenta attaches itself to the lower part of the uterus, covering part or all of the cervix. This condition is known as placenta previa, or low-lying placenta. This increases the risk of vasa previa.

Pregnancies conceived via IVF, pregnancy with multiples, and prior uterine surgeries may also increase the risk of vasa previa. Having had vasa previa in a previous pregnancy, however, does not appear to be a risk factor.

Symptoms of Vasa Previa

Vasa previa does not always cause symptoms. When it does, the main symptom is the sudden onset of vaginal bleeding, especially in the second and third trimesters. It's especially worrisome if the blood is very dark or burgundy-colored, as it could indicate that the blood is coming from the fetus, not the mother.

Diagnosing Vasa Previa

Because vasa previa is so rare, it is not intentionally screened for during pregnancy. It will usually be picked up, however, during the routine ultrasound examination performed at 18-20 weeks. If a transabdominal ultrasound, done on the outside of the belly, looks suspicious, your doctor will follow up with a transvaginal ultrasound (in which the transducer is shaped to fit inside the vagina). This, combined with a color Doppler—used to look closely at blood vessels— should confirm the diagnosis.

The condition can also be diagnosed during labor, before the membranes rupture. With vasa previa, pulsating vessels can usually be seen running across the bulging membranes upon examination of the cervix.

Treating Vasa Previa

There’s no way to prevent vasa previa. If it can be diagnosed and properly managed during pregnancy, however, it is likely the baby will survive. Typically, your provider will offer regular follow-up ultrasounds to monitor the condition closely. The aim in managing the condition is to allow the pregnancy to progress for as long as possible, ideally 35 weeks.

In some cases, your doctor may want to hospitalize you for the duration of your third trimester for close monitoring and complete bed rest. You may also be given steroids to help the baby’s lungs mature in case they need to be delivered early. Your doctors will individualize your plan of care depending on your risk factors, ultrasound findings, and other factors.

If vasa previa is present, your doctor may recommend a Caesarian section (C-section) between 35 and 37 weeks’ gestation. In a planned C-section, your surgeon will be able to adjust the type and placement of the incision according to where your placenta and your baby’s blood vessels are. If labor occurs naturally and your membranes rupture spontaneously, then your baby’s blood vessels will almost certainly rupture. If vasa previa is not diagnosed until labor has begun, you will most likely have an emergency C-section.

Early delivery carries some risk to the baby, but the risks are much lower than if vasa previa is not detected and labor progresses normally.

A Word From Verywell

Keep in mind that vasa previa, although very frightening, is very rare. When diagnosed early and accurately (even during labor), your chances of having a healthy baby are very good.

13 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Mcqueen V, Speed M, Rutter S, Gray T. Vasa praevia: Should we routinely screen high-risk women for this rare but serious condition?. Ultrasound. 2018;26(2):127-131. doi:10.1177/1742271X17747137

  2. Datta S, Babu KM, Mitra S, Patil D. Vasa Previa: An Avoidable Obstetric Tragedy. J Obstet Gynaecol India. 2016;66(3):185-7. doi:10.1007/s13224-015-0751-4

  3. Donnolley N, Halliday LE, Oyelese Y. Vasa Praevia: a descriptive review of existing literature and the evolving role of ultrasound in prenatal screening. Australas J Ultrasound Med. 2013;16(2):71-76. doi:10.1002/j.2205-0140.2013.tb00168.x

  4. American Pregnancy Association. The Fetal Life-Support System: Placenta, Umbilical Cord, and Amniotic Sac.

  5. International Vasa Previa Foundation. Vasa Previa Fact Sheet.

  6. International Vasa Previa Foundation. Bilobed and Trilobed Placentas.

  7. American Pregnancy Association. Placenta Previa.

  8. Rombauts L, Motteram C, Berkowitz E, Fernando S. Risk of placenta praevia is linked to endometrial thickness in a retrospective cohort study of 4537 singleton assisted reproduction technology births. Hum Reprod. 2014;29(12):2787-93. doi:10.1093/humrep/deu240

  9. Marr S, Ashton L, Stemm A, Cincotta R, Chua J, Duncombe G. Vasa praevia: ultrasound diagnosis at the mid-trimester scan. Australas J Ultrasound Med. 2013;16(1):8-15. doi:10.1002/j.2205-0140.2013.tb00091.x

  10. Mt. Sinai Hospital. Vasa Previa.

  11. Roberts D, Brown J, Medley N, Dalziel SR. Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth. Cochrane Database Syst Rev. 2017;3:CD004454. doi:10.1093/humrep/deu240

  12. Yerlikaya-Schatten G, Chalubinski KM, Pils S, et al. Risk-adapted management for vasa praevia: a retrospective study about individualized timing of caesarean sectionArch Gynecol Obstet. 2019;299:1545-1550. doi:10.1007/s00404-019-05125-9

  13. Jauniaux ERM, Alfirevic Z, Bhide AG, Burton GJ, Collins SL, Silver R. Vasa praevia: diagnosis and management. BJOG. 2018;27b. doi:10.1111/1471-0528.15307

Additional Reading
  • Lee, Wesley, Virginia L. Lee, Janet S. Kirk, Christopher T. Sloan, Ramada S. Smith, and Christine H. Comstock, "Vasa Previa: Prenatal Diagnosis, Natural Evolution, and Clinical Outcome." Obstetrics & Gynecology 2000. 

  • Oyelese, Yinka, and John C. Smulian, "Placenta Previa, Placenta Accreta, and Vasa Previa." Obstetrics & Gynecology 2006. 

  • Swank ML, Garite TJ, Maurel K, et al. Vasa previa: diagnosis and management. Am J Obstet Gynecol. 2016;215(2):223.e1-6. doi:10.1016/j.ajog.2016.02.044

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.