monochorionic diamniotic
Also written as: MCDA — Monochorionic Diamniotic
Twin pregnancy where fetuses share one placenta but have separate amniotic sacs.
Full Definition
Monochorionic diamniotic (MCDA) twins result from the splitting of a single embryo between days 4-8 after conception, creating two fetuses that share one placenta but develop in separate amniotic sacs. This type of twinning occurs in about 75% of monozygotic (identical) twin pregnancies. MCDA twins are at increased risk for complications due to their shared placental circulation, including twin-to-twin transfusion syndrome, selective intrauterine growth restriction, and twin anemia-polycythemia sequence. These pregnancies require specialized monitoring with regular ultrasound examinations to detect complications early. The shared placental circulation can lead to unequal blood flow distribution between the twins.
Usage
Usage note: Commonly abbreviated as MCDA in medical documentation.
In Context
- "The ultrasound confirmed monochorionic diamniotic twins with a thin dividing membrane." — First trimester ultrasound report
- "Given the monochorionic diamniotic placentation, the patient was counseled about the risk of twin-to-twin transfusion syndrome." — Maternal-fetal medicine consultation