Velamentous cord insertion is a rare pregnancy complication in which a fetus's umbilical cord doesn't properly connect to the placenta.
The placenta is a unique organ that develops when you're pregnant. It contains tissue from both the baby and mother. The exchanges of oxygen, nutrients, and waste take place in the placenta.
The umbilical cord is your baby's lifeline. It carries nutrient-rich blood and oxygen to the baby and removes waste.
The placenta attaches to the wall of the uterus, and the umbilical cord connects it to the baby. Normally, the umbilical cord is attached to the center of the placenta, but unusual placements can occur.
With velamentous cord insertion, the cord doesn't attach directly to the placenta but to other membranes in the uterus.
When this abnormality occurs, the blood vessels are naked as they pass through the membranes. They aren't protected by the umbilical cord for their full length. They also lack the protection of the gel-like substance that fills the umbilical cord and cushions the blood vessels. This lack of protection makes the blood vessels more likely to become compressed or to break.
What Causes Velamentous Cord Insertion?
The cause of velamentous cord insertion is unknown, but researchers have identified several risk factors.
It happens more often in pregnancies involving twins. It occurs in about 1% of pregnancies resulting in one child but in almost 9% of twin pregnancies. The rate is higher when the twins share a single or fused placenta.
Velamentous cord insertion is also more likely when:
- The pregnancy happens through the use of fertility treatments, such as in vitro fertilization
- The pregnancy is the mother's first pregnancy, or the expecting mother is older
- The mother smokes or has chronic diseases such as diabetes
Miscarriages that happen from the ninth to the 16th week are often associated with umbilical cord problems, including velamentous cord insertion.
What Are the Signs of Velamentous Cord Insertion?
One sign of velamentous cord insertion is vaginal bleeding, especially when you're in the third trimester. Some people don't have any symptoms.
Your doctor might use imaging and monitoring of the fetus to diagnose the condition. In the fetus, symptoms of velamentous cord insertion include a lower blood supply and a slower heart rate.
How Is Velamentous Cord Insertion Diagnosed?
Although most women have ultrasounds during their pregnancies, the place where the cord attaches to the placenta can be hard to see on ultrasounds, making it difficult to diagnose velamentous cord insertion. When velamentous cord insertion is diagnosed during pregnancy, it is usually during an ultrasound performed in the second trimester. As the baby enters the third trimester, unusual cord insertions can be harder to detect.
If you or your baby have unusual symptoms during pregnancy, it can also lead to a diagnosis. The mother may have vaginal bleeding, or the baby may have a slow heart rate. If such symptoms occur, the doctor may order extra ultrasounds, leading to the diagnosis of an unusual cord insertion.
Special technology can increase the detection rate of a velamentous cord insertion. A color Doppler ultrasound can detect velamentous cord insertion with 99% accuracy in a research setting. Standard ultrasounds are less likely to find unusual cord placements.
Vasa Previa Due to Velamentous Cord Insertion
Velamentous cord insertion can cause vasa previa — a condition where the unprotected blood vessels lie between the baby and the mother's birth canal. It happens in about 6% of velamentous cord insertion pregnancies. When labor begins, the blood vessels may break, putting the baby at risk of serious blood loss. If the blood vessels don't break, the baby can still suffer a lack of oxygen due to pressure on the blood vessels.
If the unusual cord insertion is diagnosed before delivery, doctors usually monitor the baby's health using nonstress testing. These tests check the baby's heart rate as the baby moves. The results give information about the baby's oxygen supply. Such tests are called nonstress because no extra strain is put on the baby.
When doctors diagnose vasa previa, they may take the following steps:
- Monitor the baby beginning at around 28 weeks, often performing twice-weekly nonstress tests
- Offer hospital admission at around 30 or 32 weeks for continuous monitoring or for more frequent tests
- Use corticosteroids to help the baby's lungs develop
- Schedule a C-section sometime after 34 weeks
- Perform an emergency C-section if the membranes break or if there is significant vaginal bleeding
What Are Other Complications of Velamentous Cord Insertion?
Other outcomes are possible with velamentous cord insertion. Low birth weight is one of the most common. Some studies suggest that babies with velamentous cord insertion are more likely to be delivered early and need care in a neonatal intensive care unit (NICU). Also, babies may have lower scores on the Apgar, a test used to measure a baby's health at birth.
Velamentous cord insertion can cause problems for mothers, too. They are more likely to have a hemorrhage (uncontrolled bleeding). The placenta may need to be removed by hand instead of naturally. Some curettage or scraping of the uterus may be necessary.
FAQs About Velamentous Cord Insertion
What is the survival rate for a VCI pregnancy?
If detected early, you can prevent the complications that come with velamentous cord insertion (VCI). But VCI pregnancies carry a risk of death that is three times higher than in pregnancies without VCI. If VCI is undiagnosed, the survival rate drops from 97% to 44%.
What is the difference between velamentous and marginal cord insertion?
In marginal cord insertion, the cord attaches to the edge of the placenta, which can cause some problems. In velamentous cord insertion, the cord attaches to other membranes in the uterus instead of the placenta.
Can you go full term with velamentous cord insertion?
Yes, if velamentous cord insertion is managed correctly and monitored well, many pregnancies end with healthy babies.
