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The placenta is your baby’s lifeline. As the only transient organ in the body, the placenta delivers oxygen and nutrients from mother to baby and filters metabolic waste from the baby back to the mother via the umbilical cord, without mixing the two. Pretty amazing, right?

When the umbilical cord attaches in a place other than the center of the placenta, it can sometimes throttle the flow of nutrients to the baby, resulting in adverse outcomes like low birth weight, preterm delivery, or even stillbirth.

While marginal cord insertion is rarely a cause for alarm, it does enhance certain risks to mother and baby and usually requires close monitoring. Here’s what you need to know.

What Is Marginal Cord Insertion?

Marginal cord insertion is an abnormal attachment of the umbilical cord to the placenta in which the cord is attached less than 2cm from the edge of the placenta. It is seen in roughly 7%-20% of single births and up to 25% of multiple births, though statistics vary a bit between studies [*].

The concern with a marginal cord insertion is that the placenta is thinner at its edges than in the center, so when the cord attaches near the edges, it has less support. A marginal insertion cord may also have reduced access to nutrients and blood flow, but not always.

The density of the blood vessels in placentas with abnormal cord insertion is lower than in those with normal cord insertion, which can negatively impact the transfer of nutrients [*]. One large study found that the closer the cord is to the edge — for instance, 1cm or less vs. 1-2cm — the higher the incidence of adverse perinatal outcomes [*][*].

Other Placenta Cord Insertion Types

In addition to a marginal insertion, there are three other ways the umbilical cord inserts into the placenta:

Central Cord Insertion

The umbilical cord is in the middle of the placenta, with the most access to placental tissue. This is considered normal and is seen in roughly 90% of pregnancies.

Eccentric Cord Insertion

The umbilical cord is inserted laterally but is more than 2cm from the edge of the placenta. This is abnormal but generally not a cause for alarm. However, some studies have shown an increased association with preeclampsia [*]. A cord insertion of more than 2cm but less than 3cm from the placental margin may be called a peripheral cord insertion.

Velamentous Insertion

Velamentous insertion is the most concerning type of umbilical cord insertion. Here, the umbilical cord doesn’t attach to the placenta, but instead, to the fetal (chorio-amniotic) membranes outside of it, traveling within these membranes to the placenta. The umbilical vessels in this scenario lack the protection of Wharton’s jelly in the area between the insertion point and the placental margin, making them more prone to compression or rupture [*].

Velamentous insertion is associated with three times the risk of perinatal death than in normal cord insertions as well as vasa previa, a deadly condition in which fetal blood vessels cross over or close to the internal cervical os [*]. That means that when the amniotic sac ruptures to make way for the baby, the fetal blood vessels also rupture. The fetus can bleed to death before it makes it out of the womb and the mother can experience severe hemorrhaging [*][*].

Velmanentous insertion occurs in about 1.5% -2.4% of single pregnancies and between 9-15% of multiple pregnancies [*][*].

While a marginal insertion only rarely becomes velamentous in the third trimester of pregnancy, one large Norwegian study found that the two conditions followed the same pattern of risk factors and were both risk factors of adverse outcomes, though velamentous insertion more often resulted in adverse outcomes [*].

When and How Is Marginal Cord Insertion Diagnosed?

There are no symptoms associated with a marginal cord insertion so if you have one, you’re unlikely to know unless your doctor sees it. Marginal cord insertion is usually diagnosed in the second-trimester ultrasound. Greyscale and color Doppler ultrasound can reliably detect marginal and velamentous insertions; 3D ultrasound is much less effective [*]. A diagnosis can be confirmed with MRI, which may be indicated where other anomalies are seen [*].

What Causes Marginal Cord Insertion?

We don’t know exactly what causes the umbilical cord to insert where it does, and studies show no racial or genetic disposition associated with a marginal cord insertion. It may be part of an abnormality in the early development of the placenta. However, there are a number of known risk factors that can increase your likelihood of having a marginal cord insertion. They include [*][*]:

  • Assisted reproduction technology
  • Advanced maternal age (>35)
  • Nulliparity (first child)
  • Maternal chronic diseases, such as hypertension and diabetes
  • Previous cesarean delivery
  • IUD contraception use
  • Having twins or multiples (2x-4x risk over singletons)
  • Bleeding in pregnancy
  • Female fetus
  • Previous pregnancy with anomalous cord insertion
  • Drug abuse during pregnancy

Having one or more of these risk factors doesn’t mean you’ll have a marginal or otherwise abnormal cord insertion, it merely increases the risk.

Is Marginal Cord Insertion Dangerous?

It depends. Mothers with marginal or peripheral cord insertion may face certain other complications in their pregnancy as well as their delivery, but in cases where the cord insertion does not affect the health of the placenta, studies have indicated there is no more risk to mother or infant than in pregnancies with a normal cord insertion [*].

In pregnancies where there is a placental pathology in tandem with the abnormal cord insertion, the risk of adverse outcomes is significantly elevated [*].

That said, with proper care and management, babies with marginal cord insertion can usually be carried to term and born healthy.

Marginal Cord Insertion Risks

Pregnancies that are complicated by marginal cord insertion may be at enhanced risk for other complications, particularly where the cord insertion affects the health of the placenta. These risks include [*][*][*]:

  • Placenta disorders including placenta previa and placental abruption
  • Preeclampsia
  • Nuchal cord entanglement
  • Low birth weight / small for gestational-age babies
  • Low Apgar scores
  • Preterm birth
  • Stillbirth
  • Admission to NICU
  • Emergency C-section

Marginal Cord Insertion Outcomes

While marginal cord insertion may not affect your pregnancy or the health of your baby at all — and this is usually the case — studies have associated it with increased maternal, fetal, and neonatal adverse morbidities [*].

There aren’t many studies examining the long-term health outcomes of babies born with marginal cord insertion but there are studies that indicate growth-restricted fetuses diagnosed at birth with abnormal cord insertion are at high risk for developing cerebral palsy and other developmental disorders [*].

One Chinese study divided marginal insertions by location into lower, upper, and “other” subcategories. It found that lower marginal insertions were more likely to result in low fetal weight, perhaps because the lower insertion site is closer to the cervical internal orifice, and the descending fetus may compress the umbilical cord and throttle the flow of nutrients [*].

How Is Marginal Cord Insertion Treated?

There is no treatment for marginal cord insertion but it can be managed to mitigate the potential for intrauterine growth restriction (IUGR). Your care team will take into account factors such as the location of the placenta, the size of the umbilical cord, the gestational age of the fetus, and maternal risk factors in formulating a management strategy.

In cases where marginal cord insertion is throttling fetal growth or development, your care team may recommend steroid therapy, blood transfusions, early delivery, or a C-section delivery [*].

It’s more likely you’ll just need additional monitoring from your care team.

Marginal Cord Insertion FAQ

How accurate is ultrasound in detecting marginal cord insertion?

While ultrasound is the preferred technique to identify marginal cord insertion, it may not be detailed or frequent enough to detect it. It may also depend on the sonographer’s technique and experience and the timing of the scan. Doppler ultrasound may be used to reveal blood flow patterns through the placental vessels which could lead to a more accurate diagnosis. Still, marginal cord insertion can be difficult to detect and may be missed [*].

Can marginal cord insertion correct itself?

It’s possible. The placenta moves during the course of pregnancy as the womb expands, seeking ever-better sources of blood supply.

Can non-invasive prenatal testing (NIPT) be used to diagnose marginal cord insertion?

NIPT analyzes fetal DNA in the mother’s blood to detect chromosomal abnormalities and some genetic conditions but it cannot directly assess cord insertion or fetal anatomy. Indirectly, it can detect growth restriction and abnormalities in fetal development that may be associated with marginal cord insertion [*].

Is marginal cord insertion a high-risk pregnancy?

Yes, doctors consider marginal cord insertion high risk because it has the potential to restrict the flow of blood and oxygen to the fetus.

Does marginal cord insertion require a C-section?

C-section is indicated for marginal cord insertion cases where there is a risk of heavy bleeding or fetal distress but that isn’t always the case with marginal cord insertion. It's best to consult with your care team based on your specific situation.

Can I Save Cord Blood If I Have Marginal Cord Insertion?

Yes, it’s possible to save cord blood with a marginal cord insertion, even if you’re having a C-section.

MiracleCord helps parents keep their cool in times of real stress — like when their family is facing a life-threatening illness that can be treated with a stem cell transplant. To date, there are more than 80 FDA-approved stem cell treatments for blood cancers, immune system disorders, and metabolic disorders.

Find out why we were awarded Best U.S. Cord Blood Bank by Global Health & Pharma and download our Free Info Kit to learn more about cord blood.

The Bottom Line

First things first: If you’ve been diagnosed with a marginal cord insertion, don’t panic — be glad it was caught! The diagnosis can help anticipate other complications you’re more likely to have with a marginal cord insertion as well as ensure that it is monitored and managed for the health of your baby.

Remembering that most marginal cord insertions don’t cause problems for mother or baby may help you not stress over it.

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