By on August 3, 2023

vasa previa mfm

Vasa Previa is a relatively uncommon complication that patients should be aware of but should not cause excess concern as most cases can be managed without complications. Whether you have been diagnosed with vasa previa or simply want to be as informed as possible through your pregnancy, the team at Maternal Fetal Medicine Specialists in New York can help answer any questions. Below are some of the basics that you should know about vasa previa.

What is Vasa Previa?

In vasa previa, fetal blood vessels are present in the membranes covering or near the cervix, which is the opening to the uterus. The baby comes through the cervix once the opening is completely dilated. There are three basic types of vasa previa. In type I vasa previa, the umbilical cord is inserted into the membranes rather than the placenta (velamentous insertion) and fetal blood vessels run within the amniotic membranes directly over or close to the cervix. In type II vasa previa, the placenta has two or more lobes with fetal blood vessels connecting them, flowing over or near the cervix.  Finally, in Type III one or more large boomerang vessels that run through the membranes along the margin of the placenta are present at the internal cervical opening, such as often seen with a resolved placenta previa.

The baby will pass through the cervix during delivery and if a fetal vessel is present over or near this area it can be quite dangerous for the fetus, making early detection and monitoring key. When unprotected blood vessels are over the cervix, there is a greater risk to the baby due to the possibility of a tear in the fetal blood vessels particularly after a patient’s membranes rupture, causing the baby to bleed out heavily which can lead to serious complications including death. However, with early ultrasound detection and proper management, the risk of pregnancy loss is less than 5%.

How Common is Vasa Previa?

The prevalence of vasa previa is approximately 1 in 2500 deliveries but is much higher in pregnancies conceived following use of assisted reproductive technologies such as in vitro fertilization (IVF). For IVF pregnancies, prevalence is as high as 1 in 202. The prevalence is also increased in second-trimester low-lying placentas or placenta previa, in which the placenta is was covering the cervix (even if resolved), bilobed or succenturiate lobe placentas (other placental abnormalities) in the lower uterine segment, and multiple gestations. If a Vasa Previa is identified fetal blood vessels (arterial or venous) from the umbilical cord lie over or near the cervix.

What are the Symptoms of Vasa Previa?

Some women may not experience any symptoms with vasa previa. This condition is often diagnosed during a routine pregnancy ultrasound. In rare cases, women with vasa previa may experience painless vaginal bleeding with dark blood around the second or third trimester. If you are experiencing bleeding during pregnancy, it is vital to seek out the advice of your provider as soon as possible.

How is Vasa Previa Diagnosed?

Vasa Previa is typically diagnosed during an ultrasound evaluation and most often best seen with transvaginal imaging. If Vasa Previa is present, the ultrasound will show a fetal blood vessel either directly above or close next to the cervix. Use of 3D ultrasound technology with and without Color Flow Doppler evaluations allows for proper delineation of the course of the fetal vessels and their proximity to the internal cervical opening. While making a diagnosis, your Maternal Fetal Medicine specialist will also evaluate the placental location and placental cord insertion site. If vasa previa is found, your doctor will most likely recommend additional ultrasounds as well as vaginal ultrasounds during the second or third trimester. In approximately 20%-25% of vasa previa cases, when suspected early in pregnancy the condition can actually resolve itself, varyingly defined as the vessel being > 2 to 5 cm away from the internal opening of the cervix.. Typically, vasa previa is diagnosed between weeks 18 and 26, however, 1st trimester diagnosis has been described in the literauter. This early diagnosis is key for good outcomes with vasa previa. In the past, vasa previa was rarely diagnosed before rupture, causing significant concerns as this often leads to sudden fetal death, however, this is all now considered preventable. Today, diagnosing vasa previa during pregnancy allows your obstetrician to create the best plan possible to preserve your baby’s health and offer a better outcome.

Who is at Risk for Vasa Previa?

Vasa previa may be associated with a number of conditions, including:

  • In vitro fertilization (IVF)
  • Low lying Placenta and Placenta previa
  • Pregnancy with multiple babies
  • Bilobed or Succenturiate placentas
  • Velamentous or Marginal placental Cord insertion
  • Umbilical cord insertion in the lower third of the uterus in the 1st trimester (rarely identified but described in studies mostly)

While there is no way to reduce your risk for vasa previa, you can reduce the risk of experiencing serious complications by high resolution ultrasound screening in certified ultrasound centers when the high risk situations are present as noted above.. The earlier the diagnosis, the better the outcomes of vasa previa.

How to Manage a Pregnancy with Vasa Previa

When an expecting mother is diagnosed with vasa previa, the goal is to safely plan the timing and method of delivery. In order to avoid complications, pelvic rest is often recommended. Pelvic rest would involve avoiding inserting anything into the vagina and refraining from intercourse. A short course of steroids may be used to help the baby’s lungs mature during the pregnancy as delivery may occur prematurely. In some cases of vasa previa, the condition may resolves itself at some point through the pregnancy, particularly the earlier it has been diagnosed.  However, if this does not happen patients may require specialized plans of care including earlier delivery by cesarean section to avoid the onset of labor and rupture of membranes spontaneous.  Some other patients have a higher risk of delivering their baby early. If you show concerning symptoms such as vaginal bleeding or preterm contractions, your obstetrician may recommend immediate hospitalization. This can also apply to patients who have had previous preterm birth or who have logistical issues such as living far from the hospital or otherwise facing difficulty arriving at the hospital quickly in case of an emergency. Finally,  you may be admitted to the hospital early for close monitoring prior to the delivery usually around 32-34 wks gestation in most protocols.

How Does Vasa Previa Affect Delivery?

Once the presence of vasa previa is established, you and your doctor will often plan for a cesarean birth prior to 36-37 weeks at a hospital that is capable of caring for your baby. With a cesarean birth, your doctor can avoid the fetal risks of a vaginal birth through or near the fetal blood vessels. When this condition is detected early on, the ability for your doctor to plan and balance the risks of early delivery and risks of labor the survival rates for infants is over 95%. Many experts feel that a cesarean birth between 34 and 37 weeks (late preterm birth) often provides the healthiest result for mothers and babies. During an appointment at Maternal Fetal Medicine Associates, our specialists will explain the best plan for you, including whether a cesarean delivery will be necessary. Carnegie Imaging has been at the forefront of screening and managing this condition for the past 18 years and has published in peer-reviewed journals their experience with over 100 cases of vasa previa patients diagnosed over this time period.

Schedule an Appointment

If you are pregnant or considering becoming pregnant, schedule an appointment at Maternal Fetal Medicine Associates by calling (212) 235-1335 or contacting us online. Our obstetricians will be happy to answer any questions you may have about vasa previa or other health concerns through pregnancy. For more information, visit our blog page or contact us today!


“Diagnosis and management of vasa previa” Society for Maternal Fetal Medicine https://www.smfm.org/publications/215-diagnosis-and-management-of-vasa-previa

“Frequency of spontaneous resolution of vasa previa with advancing gestational age” Carnegie Imaging https://www.carnegieimaging.com/blog/ci-publications/frequency-of-spontaneous-resolution-of-vasa-previa-with-advancing-gestational-age/

Manisha Gandhi, Jane Cleary-Goldman, Lauren Ferrara, Doina Ciorica, Daniel Saltzman, Andrei Rebarber. The association between vasa previa, multiple gestations, and assisted reproductive technology Am J Perinatol . 2008 Oct;25(9):587-9. doi: 10.1055/s-0028-1090584. Epub 2008 Oct 10.

Andrei Rebarber 1 , Cara Dolin, Nathan S Fox, Chad K Klauser, Daniel H Saltzman, Ashley S Roman Natural history of vasa previa across gestation using a screening protocol J Ultrasound Med. 2014 Jan;33(1):141-7. doi: 10.7863/ultra.33.1.141.

Maternal Fetal Medicine blogs are intended for educational purposes only and do not replace certified professional care. Medical conditions vary and change frequently. Please ask your doctor any questions you may have regarding your condition to receive a proper diagnosis or risk analysis. Thank you!

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