Marginal Cord Insertion

Marginal cord insertion is attachment of the umbilical cord to the placenta within 2 cm of its edge. It results from eccentric implantation. It matters because it is associated with a modest rise in growth restriction, preterm birth, abnormal heart rate tracings and stillbirth, though most outcomes are normal.

• Risk factors: assisted conception, multiple pregnancy, advanced maternal age, smoking, previous uterine surgery.
• Risk is higher when the insertion lies within 1 cm of the edge.
• It can occur with velamentous insertion in one pregnancy.

Women have no symptoms. Examination is usually normal, and the finding comes from the anomaly scan.

• Normal fundal height in most.
• Reduced fetal movements may signal compromise.
• Differential diagnosis: central cord insertion, battledore placenta, velamentous cord insertion, furcate insertion, circumvallate placenta.
• Complications: fetal growth restriction, preterm birth, abnormal fetal heart rate in labour, caesarean section, low birth weight, cord avulsion at delivery.

The approach is ultrasound with colour Doppler to measure the distance from the cord insertion to the placental edge.

• Ultrasound at 18 to 22 weeks: cord insertion less than 2 cm from the placental margin, with colour Doppler to show the vessels entering the disc.
• Check for vessels running over the membranes (velamentous) and over the os (vasa previa).
• Growth scans at 28 and 32 weeks; umbilical artery Doppler if growth falls.
• Examination of the delivered placenta to measure the distance from the edge.

The principle is growth surveillance, careful intrapartum monitoring and gentle cord handling.

• Supportive: reassure; stop smoking and alcohol; daily fetal movement counts; birth in a facility able to do caesarean section.
• Pharmacological: aspirin 150 mg oral at night from 12 weeks to 36 weeks if uterine artery Doppler is abnormal or other risk factors for preeclampsia exist; ferrous sulphate 200 mg oral 8-hourly for anaemia; betamethasone 12 mg IM twice, 24 hours apart, between 24 and 34 weeks and 6 days if preterm delivery is likely; oxytocin 10 IU IM at birth.
• Procedures: growth scan every 4 weeks from 28 weeks; delivery at 39 to 40 weeks for normal growth, earlier for growth restriction or abnormal cardiotocography; continuous cardiotocography in labour; controlled cord traction with the uterus guarded.
• Red flags: reduced fetal movements, falling growth centile, abnormal Doppler, abnormal cardiotocography, bleeding at rupture of membranes.
• Follow-up: antenatal review every 2 to 4 weeks; growth scans every 4 weeks; placental histology after birth.