monochorionic diamniotic
Type of twin pregnancy where twins share a placenta but have separate amniotic sacs, carrying higher complication risks.
Full Definition
Monochorionic diamniotic (MCDA) twins share a single placenta but have separate amniotic sacs, occurring in approximately two-thirds of monozygotic twin pregnancies when embryonic splitting occurs between days 4-8 after conception. This type of twinning carries significant risks due to vascular anastomoses within the shared placenta, which can lead to unequal blood distribution between the twins. Complications include twin-to-twin transfusion syndrome (TTTS), selective intrauterine growth restriction, twin anemia-polycythemia sequence, and increased risk of single fetal demise with potential neurologic injury to the surviving twin. MCDA pregnancies require specialized monitoring with serial ultrasounds every 2-3 weeks starting at 16 weeks gestation to detect early signs of complications.
Usage
Usage note: Higher risk than DCDA twins; requires specialized monitoring protocols.
In Context
- "Monochorionic diamniotic twins require intensive surveillance for TTTS starting at 16 weeks." — Maternal-fetal medicine consultation
- "The T-sign confirmed monochorionic diamniotic twinning with shared placental circulation." — Ultrasound interpretation