What are the pathophysiology, diagnosis, management, and complications of Monoamniotic (Monochorionic-Diamniotic) twins with umbilical cord entanglement?

From the Guidelines

Monoamniotic twins with umbilical cord entanglement require intensive fetal surveillance and planned delivery via cesarean section between 32-34 weeks gestation to balance prematurity risks against the increasing risk of sudden fetal death. The pathophysiology of monoamniotic twins involves the absence of a dividing membrane between twins, allowing free movement within the shared amniotic cavity, which leads to intertwining of umbilical cords and potentially causes compression of vessels, restricting blood flow, and leading to fetal compromise or death 1. Diagnosis is primarily made through ultrasound examination, which can identify the absence of a dividing membrane between twins and visualize cord entanglement using color Doppler imaging, with additional diagnostic features including visualization of both cords entering a single placental site and twins in close proximity without a separating membrane 1. Management requires intensive fetal surveillance starting at viability (around 24-26 weeks), including frequent ultrasounds and non-stress tests 2-3 times weekly or daily monitoring in an inpatient setting, with antenatal corticosteroids administered for fetal lung maturity 1. Some key points to consider in the management of monoamniotic twins include:

• Intensive fetal surveillance starting at viability
• Frequent ultrasounds and non-stress tests
• Antenatal corticosteroids for fetal lung maturity
• Planned delivery via cesarean section between 32-34 weeks gestation Complications of monoamniotic twins include sudden fetal death due to acute cord compression, twin-to-twin transfusion syndrome, intrauterine growth restriction, preterm birth, and increased risk of congenital anomalies, with a perinatal mortality rate significantly higher than other twin pregnancies, estimated at 10-20% even with modern surveillance techniques 1. It is essential to prioritize the health and well-being of both the mother and the fetuses, and to make management decisions based on the most recent and highest-quality evidence available, such as the recommendations from the Society for Maternal-Fetal Medicine 1.

From the Research

Pathophysiology

• Monoamniotic twins are at risk of unique and serious complications, including cord entanglement, which can lead to perinatal mortality 2.
• Cord entanglement is a severe complication in monoamniotic multiple pregnancies, and can be detected early in gestation using color Doppler and pulsed Doppler velocimetry 3.
• The presence of superficial artery-to-artery and vein-to-vein anastomoses and deep arteriovenous shunts can contribute to the development of complications in monoamniotic twins 3.

Diagnosis

• Early diagnosis of cord entanglement is feasible using ultrasound, and can be detected as early as 10 weeks gestation 3, 4.
• Color Doppler and pulsed Doppler velocimetry can be used to detect cord entanglement, and weekly follow-up with special observation of fetal behavior and use of color Doppler velocimetry can help monitor the pregnancy 3.
• Specific criteria are employed during ultrasonography to make the diagnosis of monoamniotic twins, and regular antepartum fetal heart trace monitoring and serial sonograms with umbilical artery Doppler flow study can help identify potential complications 5.

Management

• Optimal management of monoamniotic twin pregnancies includes early diagnosis, screening for fetal anomalies, surveillance for twin-twin transfusion syndrome, and decisions related to monitoring after viability 2.
• Regular antepartum fetal heart trace monitoring and serial sonograms with umbilical artery Doppler flow study can help identify potential complications, and hospital admission for fetal monitoring upon discovery of a cord entanglement at a viable gestation is advocated 5, 6.
• Delivery at 32 weeks is generally recommended to reduce the risk of intrauterine deaths related to cord entanglement, and Cesarean section is the preferred mode of delivery 5, 6.

Complications

• Cord entanglement is a major complication of monoamniotic twin pregnancies, and can lead to perinatal mortality 2, 6.
• Other complications associated with monoamniotic twins include congenital anomalies, twin-twin transfusion syndrome, intrauterine growth retardation, and preterm delivery 5.
• Intrauterine death of both twins can occur due to cord entanglement, and the risk of unexpected fetal demise is high in monochorionic monoamniotic twin pregnancies 3, 4.