Monoamniotic twins are twins within the same amniotic cavity (same sac). Because they also share a common placenta, they are monochorionic-monoamniotic (MCMA)
What are monoamniotic twins?
Monoamniotic twins are twins within the same amniotic cavity (same sac). Because they also share a common placenta, they are monochorionic-monoamniotic (MCMA). MCMA twins represent approximately 1% of all monozygotic (identical) twins. Presumably, they result from splitting of the embryo on day 8-9 after conception.
How are MCMA twins diagnosed?
MCMA twins are diagnosed antenatally with ultrasound by noting two fetuses without an intervening dividing membrane. In addition, only one yolk sac is present. The absence of a dividing membrane allows the fetuses to move freely within the amniotic cavity. This characteristic is important to differentiate MCMA twins from TTTS with a stuck twin, in which the dividing membrane may be difficult to see.
What are the complications of MCMA twins?
MCMA twins have a increased risk for adverse pregnancy outcome, which can be as high as 40-50%. The complications result from a number of complications, including:
How can MCMA twins be treated?
Depending on the gestational age at which MCMA twins are diagnosed, delivery may be an option. If the diagnosis is made far from viability, different treatment options have been proposed, including:
Our group specializes in the assessment, counseling and management of patients with high-risk pregnancies in Florida.