Why does chorionicity matter?

Twins can be identical (from one fertilised egg splitting) or fraternal (from two separate eggs). What matters most for monitoring is chorionicity — whether the twins share one placenta (monochorionic) or have separate placentas (dichorionic). This is best determined on an early ultrasound, ideally in the first trimester, since it becomes harder to tell later in pregnancy.

What is TTTS?

Twin-to-Twin Transfusion Syndrome (TTTS) is a condition that can affect monochorionic twins who share a placenta. Blood vessels within the shared placenta can create an imbalance, where one twin receives too much blood flow and the other too little. This needs careful monitoring, because it can progress if not caught early.

How is a twin pregnancy monitored?

  • An early scan to confirm chorionicity
  • Regular growth scans to check both babies are developing at similar, healthy rates
  • Doppler studies to assess blood flow, particularly important for monochorionic twins
  • More frequent monitoring overall compared to a single pregnancy, especially for monochorionic twins

What happens if TTTS is suspected?

If signs of TTTS are identified, Dr. Chandak will discuss the findings with you and your obstetrician. Mild, early findings are sometimes monitored closely with more frequent scans. More significant TTTS needs prompt referral to a specialist fetal therapy centre equipped for procedures such as laser treatment of the shared placental vessels — this is a highly specialised intervention performed at select tertiary centres, and we will guide and support that referral pathway if it's ever needed.

Frequently asked questions

Twin pregnancies generally need closer monitoring than a single pregnancy, and monochorionic (shared-placenta) twins need particularly close attention because of the risk of TTTS.

Mild cases are sometimes managed with close monitoring. More significant TTTS is treated at specialist fetal therapy centres, often with laser treatment of the connecting placental vessels — we will support and guide referral to the right centre if this is needed.

Ideally in the first trimester, since it becomes progressively harder to distinguish monochorionic from dichorionic twins as pregnancy advances.