From the Guidelines
Mono mono twins are identical twins who share both the same amniotic sac and placenta in the womb, occurring in only about 1% of twin pregnancies and requiring intensive monitoring due to significant risks. These pregnancies are considered high-risk due to complications such as cord entanglement and compression, which can lead to fetal death 1. The management of mono mono twins typically involves frequent ultrasounds, often twice weekly, starting at around 16 weeks, with hospitalization recommended between 24-28 weeks until delivery 1. Key aspects of their care include:
- Frequent ultrasounds for monitoring
- Hospitalization between 24-28 weeks
- Planned delivery via cesarean section between 32-34 weeks gestation
- Administration of corticosteroids before delivery to mature the babies' lungs The survival rate for mono mono twins has improved significantly with modern medical care, now reaching over 90% when properly managed with close surveillance 1. This improvement is attributed to early diagnosis, serial ultrasound, and antenatal surveillance 1. The primary complication unique to this type of twin pregnancy is the entanglement of the twins' umbilical cords as they move freely within the same sac, highlighting the need for specialized care.
From the Research
Definition of Monochorionic-Monoamniotic (Mono Mono) Twins
- Monochorionic-monoamniotic (mono mono) twins are a rare type of twin pregnancy where two fetuses develop in a single amniotic cavity, sharing the same placenta 2.
- This type of pregnancy occurs when a single fertilized egg splits between 8-13 days after fertilization, resulting in two fetuses that share the same placenta and amniotic sac 2.
Characteristics and Risks
- Mono mono twins are at a higher risk of perinatal mortality, malformations, prematurity, and cord entanglement compared to other types of twin pregnancies 3, 4, 2, 5.
- The risk of twin-twin transfusion syndrome, congenital anomalies, and fetal death is also increased in mono mono twins 3, 4, 5.
- Cord entanglement is a unique risk in mono mono twins, which can occur at any time during the pregnancy 3, 4, 2, 5.
Management and Outcomes
- Early diagnosis and close monitoring of mono mono twins are crucial to reduce the risk of complications and improve perinatal outcomes 3, 4, 2, 5, 6.
- Intensified obstetrical monitoring, hospitalization, and premature birth around 32-34 weeks of gestation are often recommended to improve outcomes 4, 2, 5, 6.
- The mode of delivery is often cesarean section, although vaginal delivery may be considered in some cases 4, 2, 5.
- Neonatal morbidity is high in mono mono twins, mainly due to prematurity, and close monitoring and care are necessary to ensure the best possible outcomes 4, 5.