Marginal Umbilical Cord Insertion

The placenta and umbilical cord are the lifelines between mother and baby during pregnancy. The umbilical cord attaches to the placenta and enables the delivery of maternal oxygen and nutrients to the baby. The proper functioning of this delivery system is critical to fetal development.

The umbilical cord insertion (or attachment) to the placenta is a key part of this delivery system. There are 4 different types of umbilical cord insertions to the placenta. Only 2 of these 4 types of umbilical cord insertion are considered to be abnormal: (1) marginal cord insertion; and (2) velamentous cord insertion. This page will focus on marginal cord insertion, which is the less dangerous of the 2 abnormal cord insertions.

What is Marginal Umbilical Cord Insertion?

Normally the umbilical cord is supposed to insert and attach to the center of the placenta (central cord insertion). A marginal umbilical cord insertion occurs when the cord attaches on the side of the placenta instead of in the middle at the central placental mass. Marginal cord insertion is considered abnormal and it occurs in roughly 9 out of every 100 pregnancies.

Marginal cord insertion is problematic because the sides of the placenta are much weaker and have less tissue compared to the central area of the placenta where the cord is supposed to insert. The weaker sidewalls of the placenta are not able to properly support the cord attachment the same way that the central placental mass can.

What Causes Marginal Cord Insertion?

The exact causes of marginal cord insertion are not understood. No causative factors have been linked to marginal umbilical cord insertion and there is no genetic, racial, or geographical predisposition associated with this condition. The one well-known risk factor for marginal cord insertion is a multiple pregnancy. Marginal cord insertions (and all abnormal cord insertions) are three to four times more likely with twin and multiple pregnancies. New research has also found that the marginal insertion of the umbilical cord is more likely when fertility treatments are used to help conceive.

Symptoms and Diagnosis of Marginal Cord Insertion

Marginal cord insertion does not result in any noticeable physical symptoms early in the pregnancy. Fortunately, abnormal insertion of the umbilical cord is fairly easy to diagnose with a prenatal ultrasound and physical examination.

Complications from Marginal Cord Insertion

Any abnormal cord insertion, including marginal cord insertion, can potentially result in placental development problems which can impact fetal development and growth. Marginal cord insertion can restrict or reduce the blood flow and circulation to the fetus during pregnancy. Reduced fetal blood flow can cause intrauterine growth restriction (IUGR) and other developmental abnormalities in the fetus.

Marginal cord insertion (and the secondary conditions it can lead to such as IUGR) can potentially result in premature birth. Some studies have found that that marginal cord insertion might increase the chances of spontaneous abortion in the 1st or 2nd trimester, but the risk increase is comparatively small. Another potential risk with marginal cord insertion is excessive bleeding during vaginal childbirth.

Marginal cord insertion can also increase the chances of developing another placental complication known as placenta previa. Placenta previa occurs when the placenta is abnormally located at the bottom of the womb and is partially or completely blocking the entrance to the birth canal.

Vasa Previa and Marginal Cord Insertion

Vasa previa is a rare but potentially dangerous condition in which fetal blood vessels are present in the amniotic sac instead of being contained within the umbilical cord. Vasa previa is a complication that is mostly related to velamentous cord insertion, but marginal cord insertion can also make vasa previa more likely.

Vasa previa can be dangerous if not diagnosed before vaginal delivery is attempted. During normal childbirth, the amniotic sac ruptures to allow the baby to travel through the birth canal. When vasa previa is present this normal rupturing of the amniotic sac can be very dangerous because the fetal blood vessels in the amniotic sac will also rupture. The result is significant blood loss for the baby. When vaginal delivery is attempted in a vasa previa pregnancy there is a very high risk that the baby will bleed to death before they are born.

Treatment of Marginal Cord Insertion

There is no effective treatment to correct marginal umbilical cord insertion. Once the umbilical cord attaches abnormally there is nothing doctors can do to correct the attachment. Marginal cord insertion can be very effectively managed to a good outcome, however, as long as the condition is timely diagnosed and carefully monitored. A C-section delivery may be advised for women with marginal cord insertion.