Your baby’s umbilical cord is his lifeline, connecting him to your placenta. Any abnormality in the way it's attached to the placenta can put a pregnancy at higher risk of complications.
A velamentous cord insertion is an umbilical cord abnormality that may require monitoring during your pregnancy, but happily, with proper care, the chances that it will end up being problematic for your pregnancy or baby are low.
What is velamentous cord insertion?
In a normal pregnancy, fetal blood vessels run via the umbilical cord directly into the placenta. But velamentous cord insertion is a complication in which the umbilical cord doesn’t insert into the placenta properly.
“Velamentous cord insertion refers to the umbilical cord inserting into the fetal membranes [surrounding the placenta],” explains Andrei Rebarber, M.D., a board-certified OB/GYN with a speciality in maternal fetal medicine, and a member of the What to Expect Medical Review Board.
To reach the placenta, the fetal blood vessels within the umbilical cord must then branch out and grow toward the placenta.
Typically, a thick, white, gelatinous substance called Wharton’s jelly encases the umbilical cord vessels to protect them, but with velamentous cord insertion, the blood vessels outside the placenta are unprotected by this substance.
This may leave the vessels more vulnerable to kinking or compression, which may disrupt the flow of blood or nutrients to the fetus, says Dr. Rebarber.
This pregnancy complication occurs in about 1% of singleton pregnancies and in up to 15% of identical twin pregnancies in which a single placenta is shared by both fetuses.[1]
It’s not entirely clear how a velamentous cord insertion happens. The good news is that it rarely causes serious problems. You’ll just need more monitoring during your pregnancy and when you’re giving birth.
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How is velamentous cord insertion diagnosed?
Your practitioner would likely diagnose velamentous cord insertion based on ultrasound images of the placenta and umbilical cord — usually performed during the second trimester. (In some cases, your doctor may detect it in a first trimester scan.)
“It’s part of the standard anatomical survey at 20 weeks to look at the cord insertion into the placenta to make sure that it’s appropriate,” says Dr. Rebarber. He says diagnosis is 95 to 100% accurate once this abnormality is observed on a scan.
During this 20-week scan, if a velamentous cord insertion is identified, your physician will also check to rule out vasa previa, which can make velamentous cord insertion much more dangerous.
Vasa previa occurs when the exposed umbilical vessels run across or very near to the cervix, which makes them more prone to rupturing. This can lead to fetal hemorrhage and possibly death, according to the American Journal of Obstetrics and Gynecology. [2]
It can be scary to get a velamentous cord insertion diagnosis, but you're not alone. Connect with other parents who have experienced pregnancy complications in the What to Expect app.
When does velamentous cord insertion typically happen?
Experts don’t know the exact timeline of when the cord abnormally inserts. But it’s usually detected during a second trimester ultrasound.
Who is most at risk of having a velamentous cord insertion?
Pregnant women have a greater chance of developing this condition if they:
- Have placenta previa (a low-lying placenta)
- Are carrying monochorionic twins (identical twins who share a single placenta)
- Have undergone IVF to get pregnant
- Are over 35 years old at the time of delivery
What pregnancy complications can occur if you have velamentous cord insertion?
Complications resulting from velamentous cord insertion are rare, but they can happen and include:
- Compression or rupture of umbilical cord blood vessels. Because the umbilical cord blood vessels closest to the placenta are unprotected in a velamentous cord insertion, the vessels are at slightly higher risk of compression or rupture. This is especially true when these vessels are located close to the cervix, as they might be if you also have vasa previa.
- Emergency C-section. There is also an increased chance of needing an emergency C-section, as the unprotected vessels during labor may result in the baby showing signs of distress on the fetal heart rate monitors.
- Manual removal of the placenta after delivery. Some women with velamentous cord insertion end up needing to have their placenta manually removed after they give birth because the umbilical cord is more fragile and may tear off the membranes during routine extraction.
- Hemorrhage during labor. Other women have an increased risk of hemorrhage during delivery of the placenta.
Close monitoring and top-notch medical care will help prevent these complications.
Can velamentous cord insertion hurt my baby?
The chances that this pregnancy complication will harm your baby are very low.
“I had a velamentous cord insertion with my first. She’ll be celebrating her 7th birthday [at the] end of March,” says What to Expect Community mom Sunflower891.
That said, “there are concerns about poor growth,” says Dr. Rebarber, due to potential kinking or compression of these exposed vessels. “Chronic compression is thought to be associated with in utero growth restriction.”
Velamentous cord insertion can also increase the risk of preterm birth, low Apgar score, and the need for a stay in the neonatal intensive care unit (NICU) after birth.
In twin pregnancies with velamentous cord insertion, there is a slightly higher risk of intrauterine growth restriction for one or both babies.
What can you do about velamentous cord insertion?
If an ultrasound exam suggests you have a velamentous cord insertion, you may have ultrasounds more often to monitor the condition of your baby and the placenta and make sure everything is proceeding in a healthy, safe way.
Your doctor will carefully track your baby’s growth and may recommend some form of regular fetal testing such as a nonstress test or ultrasounds.
“We do ultrasounds to assess growth every four weeks, usually starting at 24 weeks,” says Dr. Rebarber.
If everything is okay, there’s no need for your doctor to induce you early, though your practitioner likely won’t let you go longer than 40 weeks.
In the absence of vasa previa or placenta previa, it’s unlikely you would need a C-section based solely on a diagnosis of velamentous cord insertion alone.
During labor you’ll likely need continuous monitoring with a fetal heart monitor to ensure there are no complications from the abnormal cord placement.
“It’s really important to make sure that we know the baby’s heart rate is tolerating the contractions and that we’re not concerned that there may be any risk to these vessels being kinked or ruptured,” says Sonya Brar, M.D., an OB/GYN at Mount Sinai Downtown and Mount Sinai West in New York City and an instructor at the Icahn School of Medicine at Mount Sinai.
After delivery, it’s unlikely your practitioner will pull on the cord to help the placenta detach (as is done with normal cord insertions).
This may mean it could take longer to deliver the placenta after birth, but there’s no downside to that as long as you’re being monitored — and hopefully you’ll spend the time cuddling with your newborn.
“I had this with my first pregnancy. It made me super nervous as a first-time mom, and I switched from a midwife/birth center to seeing a ‘high risk’ OB/GYN,” said What to Expect Community mom Babyh22222. “I had regular ultrasounds and baby was growing well. My doctor knew to be gentle with the cord after delivery and showed me a perfectly healthy placenta at the end!”
Is there any way to prevent velamentous cord insertion?
There’s no way to prevent velamentous cord insertion — it’s something that happens for no apparent reason during fetal development.
Even in the unlikely case that this complication occurs during your pregnancy, know that it’s even rarer that the condition will cause any serious problems — you’ll just need more ultrasounds during your pregnancy and more monitoring during childbirth.
Velamentous cord insertion is a pregnancy complication in which the umbilical cord attaches to the membranes outside the placenta instead of to the placenta itself.
This diagnosis, typically made at the 20-week ultrasound, often results in increased pregnancy monitoring.
Complications for the mother or baby are rare, but can include low birth weight and/or manual removal of the placenta after delivery.
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