From the Guidelines
Marginal cord insertion is a condition that requires close monitoring during pregnancy, particularly in the second trimester, to assess for potential complications such as intrauterine growth restriction, preterm birth, and bleeding during delivery. This condition occurs when the umbilical cord attaches at the edge of the placenta rather than in the central portion. According to the most recent study 1, placental cord insertion of each twin should be documented in the second trimester, and marginal or velamentous cord insertion are common among monochorionic (MC) pregnancies.
Key Considerations
- The risk of adverse outcomes, including small for gestational age and intrauterine fetal demise, is increased in MC twins with velamentous cord insertion 1.
- Velamentous cord insertion in MC twins is also associated with a higher frequency of vasa previa, which can lead to acute fetal hemorrhage and death during delivery 1.
- A study by Saito et al 1 found that 27% of twin pairs with abnormal cord insertions developed twin-to-twin transfusion syndrome (TTTS) compared to 7% of twin pairs with normal cord insertions.
Monitoring and Management
- Pregnant women with marginal cord insertion should attend all scheduled prenatal appointments for ultrasound monitoring to assess fetal growth and placental function 1.
- Healthcare providers should be aware of the possibility of vasa previa, especially in monochorionic pregnancies, and perform a baseline cervical length assessment using transvaginal US to determine the risk of preterm delivery 1.
- Women with marginal cord insertion should be aware of warning signs such as vaginal bleeding or decreased fetal movement, which should prompt immediate medical attention.
Outcome and Prognosis
- Despite the increased risk of complications, most pregnancies with marginal cord insertion progress normally without complications 1.
- Regular monitoring and close surveillance can help identify potential issues early on, allowing for prompt intervention and minimizing the risk of adverse outcomes.
From the Research
Definition and Diagnosis of Marginal Cord Insertion
- Marginal cord insertion (MCI) is a condition where the umbilical cord inserts into the placenta at the edge, rather than centrally 2.
- A study found that MCI can be diagnosed when the cord insertion-to-placental edge distance is 1.0 cm or less, as this distance is significantly associated with adverse obstetric outcomes 2.
- Another study defined MCI as a distance of ≤2 cm from the cord insertion to the placental edge, and found that it is associated with increased likelihood of low birth weight, preterm delivery, and composite adverse obstetrical and neonatal outcomes 3.
Risk Factors for Marginal Cord Insertion
- A meta-analysis identified assisted reproductive technology, chronic hypertension, placenta previa, and nulliparity as significant risk factors for MCI in singleton pregnancies 4.
- The same meta-analysis found no significant associations between MCI and smoking, maternal age, prior Cesarean section, preexisting diabetes, or Caucasian ethnicity 4.
Association with Adverse Perinatal Outcomes
- MCI has been associated with increased risk of small-for-gestational-age neonates, preeclampsia, placental abruption, stillbirth, preterm delivery, and lower mean birth weight 5.
- A systematic review and meta-analysis found that pregnancies with MCI are at higher risk of adverse perinatal outcomes, including emergency cesarean delivery, 5-minute Apgar score of <7, and neonatal intensive care unit admission 5.
- Another study found that MCI is associated with increased likelihood of low birth weight, preterm delivery, and composite adverse obstetrical and neonatal outcomes 3.
Placental Basis of Fetal Growth Restriction
- Placental dysfunction is a major contributing factor to fetal growth restriction, and MCI may be a rare placental disease that contributes to this condition 6.
- The role of MCI in fetal growth restriction is not fully understood, and further research is needed to investigate the underlying pathophysiology and the effect of increased surveillance on perinatal outcomes 5.