From the Guidelines
An eccentric cord insertion on ultrasound in pregnancy refers to a condition where the umbilical cord attaches to the placenta away from the center, near the edge but not at the very margin. This condition is a relatively common finding, and while it is generally considered a normal variant, it is crucial to document it during ultrasound examinations and distinguish it from marginal or velamentous cord insertions, which carry higher risks 1. The position of cord insertion is significant because it affects the blood distribution pattern throughout the placenta, and an eccentric insertion may alter this pattern but usually remains adequate for fetal development. Key points to consider include:
- Eccentric cord insertion should be documented during the second trimester, specifically during the fetal anatomy scan at 18 to 22 weeks’ gestation 1.
- It is essential to differentiate eccentric cord insertion from marginal or velamentous cord insertion, as the latter conditions are associated with increased risks of adverse outcomes, including small for gestational age, intrauterine fetal demise, and vasa previa 1.
- Healthcare providers will typically continue routine monitoring without changing the pregnancy management plan for eccentric cord insertion alone, but may pay closer attention to fetal growth parameters during subsequent ultrasounds. In the context of multiple gestations, such as monochorionic (MC) twins, the risk of velamentous cord insertion is higher, and this condition is associated with increased risks of twin-to-twin transfusion syndrome (TTTS) and discordant growth 1. Therefore, accurate documentation and monitoring of cord insertion are critical in pregnancy, especially in high-risk cases like MC twins, to ensure optimal fetal development and minimize potential complications.
From the Research
Definition of Eccentric Cord Insertion
- An eccentric cord insertion refers to the attachment of the umbilical cord to the placenta in a location that is not central, but not marginal or velamentous either 2.
- This type of cord insertion is often described as being located more than 1 cm away from the nearest placental edge, but not as far out as a marginal insertion, which is typically defined as being within 1 cm of the placental edge 3, 4.
Identification of Eccentric Cord Insertion on Ultrasound
- Eccentric cord insertion can be identified on ultrasound by measuring the distance from the cord insertion site to the nearest placental edge 3, 4.
- A distance of more than 1 cm is generally considered normal, while a distance of 1 cm or less is considered abnormal and may indicate a marginal or velamentous cord insertion 3, 4.
- Color Doppler imaging may be used to help distinguish between different types of abnormal cord insertions, such as marginal and velamentous insertions 3.
Clinical Significance of Eccentric Cord Insertion
- Eccentric cord insertion has been associated with reduced placental efficiency and lower birth weight, although the exact mechanisms are not fully understood 5.
- Abnormal cord insertions, including eccentric insertions, have been linked to increased risk of fetal growth restriction, oligohydramnios, and placental abruption 4, 6.
- However, the clinical significance of eccentric cord insertion is not as well established as that of marginal or velamentous insertions, and further research is needed to fully understand its implications 2, 6.