This is a complication of identical twins that affects thousands of pregnancies every year in the United States. When identical twins share a single placenta (also called the afterbirth), they are called monochorionic. Sometimes, triplets can be identical, all sharing a single placenta, also called monochorionic. TTTS affects up to 16% of monochorionic pregnancies. The key factor giving a risk for TTTS is the single shared placenta.
Marked size difference small donor on the left
In the past decade, our understanding of the causes and effects of TTTS has expanded rapidly. Recent advances in ultrasound assessment allow us to detect TTTS early in pregnancy and dramatic improvements in technology mean we can now treat this condition inside the uterus.