Twins: MCDA (Monochorionic)

In MCDA twins, 'monochorionic' means one chorion (placenta). On ultrasound before 14 weeks, we identify this by the 'T sign'—a very thin membrane that meets the placenta at a 90-degree angle, without the thick wedge seen in DCDA twins. Because the babies share a single blood pool, their destinies are linked; what happens to one can affect the blood pressure and oxygen levels of the other.

MCDA twins are at risk for specific 'shared-placenta' complications:

• TTTS (Twin-to-Twin Transfusion Syndrome): When one baby sends too much blood to the other.
• sFGR (Selective Fetal Growth Restriction): When the placenta is shared unequally, and one twin becomes much smaller.
• TAPS (Twin Anemia Polycythemia Sequence): A slow, chronic blood transfusion between the babies.
• Sudden Events: Because of the connected vessels, if one baby experiences a sudden event, the other is at immediate risk.

The management of MCDA twins relies on frequent, high-resolution ultrasound:

1. Bi-weekly Scans: Starting at 16 weeks, we scan every 14 days without exception.
2. Amniotic Fluid Check: Measuring the 'Deepest Vertical Pocket' (DVP) in each sac to check for TTTS.
3. Bladder Assessment: Confirming both babies have visible bladders.
4. Doppler Studies: Checking the blood flow in the brains and umbilical cords of both babies.

Our care follows the highest international standards:

• Standardized Reporting: Every scan tracks the difference in weight and fluid between the twins.
• Fetal Surgery Readiness: If TTTS or TAPS is detected, we are one of the few centers in the region capable of performing Fetoscopic Laser Ablation to separate the shared blood vessels.
• Cervical Surveillance: Monitoring the mother for signs of early labor, which is more common in twin pregnancies.

With early detection, most shared-placenta twins have a safe arrival:

• Timing: We typically recommend delivery at 36 weeks. Waiting longer increases the risk of placental insufficiency in these shared gestations.
• Mode of Delivery: If both babies are growing well and the first twin is head-down, a vaginal birth is possible. However, the threshold for a C-section is lower than in singleton pregnancies to ensure the safest exit for both twins.

If your early scan shows 'identical' twins or 'single placenta,' you should be referred to a fetal medicine specialist immediately.

Dr. Werner Diehl and Dr. Ali Al-Ibrahim specialize in monochorionic twin pathology. We provide the bi-weekly, high-precision scans necessary to identify complications early and the surgical expertise to treat them if they occur.