What Is Velamentous Cord Insertion?

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A velamentous cord insertion is when the umbilical cord is abnormally inserted into the placenta. This is a rare complication. In a normal gestational sac, the umbilical cord is inserted into the middle of the placenta (central insertion) and entirely enclosed in the amniotic sac. The baby's blood vessels travel from the center of the placenta into the baby via their umbilical cord.

In a velamentous insertion, the umbilical cord inserts itself into the amniotic membrane rather than in the placenta. The baby's blood vessels stretch along the membrane between the insertion point and the placenta. As such, the vessels are unprotected because the substance that typically surrounds them, Wharton's jelly, is missing.

The cause of velamentous cord insertion is unknown, and this abnormality is not the only one of its kind. There is also the possibility of a marginal insertion, in which the placement of the umbilical cord is less than 2 centimeters sideways of the placental margin, or edge of the placenta. Occurring in about 7% of single-baby pregnancies, a marginal cord insertion can develop into a velamentous insertion.

Signs of Velamentous Cord Insertion

There are several signs that may indicate velamentous cord insertion. One such indicator, which may be detected by your healthcare provider during a routine ultrasound, is a decrease in fetal blood supply.

If a fetus is not hitting developmental milestones during your prenatal appointments, it could be another sign that there is a complication like a velamentous cord insertion. Additionally, if you experience bleeding during pregnancy, bring this to the attention of your doctor or midwife.


Velamentous cord insertion can be diagnosed through an ultrasound. It may be difficult to see during the first trimester of pregnancy, but it is easier to detect during the second trimester.


Velamentous insertion occurs in 1.1% of single-baby pregnancies and 8.7% of twin pregnancies. This type of insertion is more common earlier in pregnancy. In cases of miscarriage, velamentous cord insertion happens around 33% of the time when the pregnancy ends between nine and 12 weeks gestation. In pregnancies that end between 13 and 16 weeks, the rate is a little lower at 26%.


Risk factors for developing a velamentous cord include having a two-lobed placenta, uterine anomalies, and the fetus having a single umbilical artery. Other risk factors to consider are:

  • Advanced maternal age
  • Having a female fetus
  • Having twins
  • Pregnancies conceived with assisted reproductive technology like in vitro fertilization (IVF)
  • Prior abnormal cord insertion in pregnancy


Velamentous cord insertion can lead to complications for the fetus. Once the baby is born, they may be more likely to be transferred to the neonatal intensive care unit (NICU). They may have a low Apgar score (a ranking of a baby's physical condition), an abnormal heart rate, or other physical issues.

Although rare and less of a risk when properly monitored, velamentous insertion also increases the risk of stillbirth. There are additional complications of which expecting parents should be aware too.

Vasa Previa

Velamentous cord insertion could result in a potentially serious pregnancy complication called vasa previa. Vasa previa occurs when the baby's blood vessels run close to the inner part of the cervix—the tissue that separates the uterus from the vagina.

Because of their location, the baby's blood vessels are at risk of rupturing. The condition can be fatal, with approximately 50% of undiagnosed cases leading to fetal death. Approximately 6% of single-baby pregnancies with velamentous cord insertion will also have vasa previa.

If vasa previa is detected during pregnancy with an ultrasound, there is a 97% to 99% chance that the baby will survive. Once diagnosed, the pregnant person will be scheduled to deliver the baby by Cesarean section at around 34 - 37 weeks gestation.

Small for Gestational Age

A velamentous cord can restrict fetal growth. As a result, it increases the chances of having a newborn who is small for gestational age (SGA). These babies may be less developed or weigh less than a typical infant of the same age. SGA can also lead to issues in newborns, such as:

  • Hypoglycemia (low blood sugar)
  • Polycythemia (high red blood cell counts)
  • Hyperbilirubinemia (which may cause seizures/brain damage)
  • Hypothermia (low body temperature)


Preeclampsia could become an issue for pregnant people with velamentous cord insertion. Hallmarks of this disease are high blood pressure (hypertension) and failure of the liver and/or kidneys. If detected during early pregnancy, it is possible for certain medications to be prescribed to mitigate the effects of preeclampsia. Delivering the baby is the only way to end preeclampsia, and so a planned preterm birth may be required.

Premature Birth

Velamentous cord insertion may necessitate a preterm delivery. This could entail the pregnant person being induced for labor earlier than anticipated, or it could involve a C-section birth. Placental implantation abnormalities, including velamentous cord insertion, are the cause of 5.6% to 8.7% of preterm deliveries.

Emergency Cesarean Section

A 2020 study of more than 500 cases of velamentous cord insertion noted that 16.1% of the pregnant people involved required an emergency C-section. Early detection of a cord abnormality via ultrasound can reduce the likelihood of an emergency Cesarean, pending an otherwise low-risk pregnancy.


Although there is no known prevention or treatment for velamentous cord insertion, the best course of action, once it is discovered, is to get regular ultrasounds and closely monitor the fetus. Your healthcare provider may also suggest a nonstress test in the third trimester. This comprises wearing a belt with built-in sensors and tracking the baby's movement and heart rate.

Frequently Asked Questions

Why does velamentous cord insertion happen in multiple pregnancies?

It is not known why velamentous cord insertion occurs in multiple pregnancies, but it does happen more often in multiple than in singleton pregnancies.

Does velamentous cord insertion affect a baby’s brain?

A velamentous cord insertion can indirectly lead to brain damage in two ways. During childbirth, the baby's blood vessels may tear, preventing the baby from getting enough oxygen. This event, called hypoxic ischemic encephalopathy (HIE), can lead to brain damage. Around 39% of HIE cases involve velamentous or marginal cord insertion.

A velamentous cord insertion can also restrict fetal growth. Babies who are small for gestational age are also at risk for a condition called hyperbilirubinemia. This can lead to brain damage that occurs in utero. However, keep in mind that a velamentous cord insertion is a rare occurrence, and so brain damage is not likely.

Can velamentous cord insertion correct itself?

No, velamentous cord insert cannot correct itself.

Can velamentous cord insertion cause birth anomalies?

Yes, velamentous cord insertion can cause birth anomalies such as an abnormal heart rate, a baby being small for gestational age, and other complications associated with preterm birth should an early delivery be required.

A Word From Verywell

Velamentous cord insertions may pose serious complications for parent and child, but it is important to remember that they are rare. When they do happen, there is still a good chance of a positive outcome with close monitoring. If you have concerns, be sure to speak with your healthcare provider to determine the best course of action for your pregnancy.

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