From the Guidelines
Monochorionic monoamniotic (MoMo) twin pregnancies require intensive prenatal care due to their high-risk nature, with perinatal mortality rates of 10-20%. Management should include early referral to maternal-fetal medicine specialists and frequent ultrasound monitoring starting at diagnosis, as recommended by the Society for Maternal-Fetal Medicine 1.
Key Considerations
- Ultrasounds should be performed every 2 weeks from 16 weeks until delivery to assess fetal growth, amniotic fluid, and cord entanglement, with more frequent monitoring indicated with clinical concern 1.
- Daily fetal monitoring should begin at 24-28 weeks, either through inpatient hospitalization or outpatient monitoring with non-stress tests 1-2 times daily.
- Antenatal corticosteroids (betamethasone 12mg IM, two doses 24 hours apart) should be administered at 24 weeks to accelerate fetal lung maturity.
- Delivery timing is crucial, with planned cesarean delivery recommended between 32-34 weeks after corticosteroid administration to balance prematurity risks against the increasing risk of intrauterine fetal demise in the third trimester, as suggested by recent guidelines 1.
Rationale
This intensive monitoring approach is necessary because MoMo twins share both a placenta and amniotic sac, creating risks of cord entanglement, twin-twin transfusion syndrome, and sudden fetal death that increase with advancing gestation 1. The most recent and highest quality study, published in 2024, emphasizes the importance of early diagnosis, serial sonograms, and antenatal surveillance in achieving survival rates of >90% in MC MA twins 1.
Additional Recommendations
- Routine first-trimester sonographic determination of chorionicity and amnionicity is recommended, as it can help identify high-risk pregnancies early on 1.
- Fetoscopic laser surgery is recommended as the standard treatment for stage II through stage IV twin-twin transfusion syndrome presenting between 16 and 26 weeks of gestation 1.
- Consultation with a specialized fetal care center is recommended when twin anemia-polycythemia sequence progresses to a more advanced disease stage (II) before 32 weeks of gestation or when concern arises for coexisting complications such as twin-twin transfusion syndrome 1.
From the Research
Key Prenatal Care Considerations
- Monochorionic monoamniotic twin pregnancies are considered high-risk gestations due to the risk of cord entanglement, twin-twin transfusion syndrome, and other complications 2, 3.
- Early pregnancy ultrasound, ideally between 10 and 13 weeks' gestation, is critical for the diagnosis and characterization of twin pregnancies 2.
- Appropriate fetal surveillance should be initiated at 16 weeks' gestation and continued until delivery to improve outcomes for monochorionic twins 2.
- Surveillance for twin-twin transfusion syndrome, decisions related to monitoring after viability, and timing and route of delivery are all critical in managing monoamniotic twin pregnancies 3.
Management of Complications
- Cord entanglement is a unique risk in monoamniotic twin pregnancies, and early identification is crucial 4.
- Twin-twin transfusion syndrome, selective intrauterine growth restriction, and twin reversed arterial perfusion sequence are potential complications in monochorionic twin pregnancies 2.
- Malformations, prematurity, and intrauterine growth restriction are also common in monochorionic monoamniotic twin pregnancies 5.
Timing and Route of Delivery
- The timing of planned delivery is a subject of debate, but studies suggest that delivery between 32 and 36 weeks' gestation may be optimal 6.
- Inpatient surveillance is associated with similar fetal mortality as outpatient management in uncomplicated monoamniotic twin pregnancies 6.
- After 31 weeks' gestation, close monitoring is necessary to prevent intrauterine fetal deaths and neonatal deaths 6.