Velamentous Cord Insertion Pregnancy Complications

Pregnant woman wearing a hospital gown holding her belly

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A velamentous cord insertion is a pregnancy complication in which the umbilical cord is abnormally inserted into the placenta. In a typical pregnancy, a baby's blood vessels travel from the center of the placenta into the baby via their umbilical cord. With a velamentous cord insertion, the baby's blood vessels are unprotected. The substance that typically surrounds them (Wharton's jelly) is missing.

In a normal gestational sac, the umbilical cord is inserted into the middle of the placenta and entirely enclosed in the amniotic sac. In a velamentous insertion, the 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.

Prevalence of Velamentous Insertion

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

Velamentous Cord Insertion and Vasa Previa

Velamentous cord insertion can lead to more serious pregnancy complications, such as 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, these blood vessels are at risk of rupturing. The condition can be deadly, 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.

Velamentous cord insertion can be diagnosed through an ultrasound. It may be difficult to see during the first trimester of pregnancy, but is easier to visualize during the second trimester. If you have been diagnosed with a velamentous insertion, your doctor may want to perform a c-section.

Risk Factors and Complications

Risk factors for developing a velamentous cord include having a two-lobed placenta, uterine anomalies, and the fetus having a single umbilical artery. Aside from vasa previa, velamentous cord insertion can also lead to other complications and risks for the fetus. A velamentous cord can restrict fetal growth and increase the risk of pre-eclampsia, premature birth, and the need for a c-section.

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), low birth weight, an abnormal heart rate, or other physical issues. Velamentous insertion also increases the risk of having a stillborn child.

Other Types of Cord Insertions

In addition to velamentous cord insertion, there are several other ways the umbilical cord can join with the placenta.

  • Central insertion: Normal umbilical placement in the center of the placenta; about 90% of pregnancies
  • Marginal insertion: Placement less than 2 cm sideways of the placental margin; about 7% of pregnancies. A marginal cord insertion can develop into a velamentous insertion.
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