TTTS is a serious complication that occurs in monochorionic-diamniotic (MCDA) twin pregnancies in which blood is not evenly shared between twins across a shared placenta. This places the pregnancy at high risk for premature birth, serious illness for one or both twins, and possible loss of pregnancy.
TTTS complicates approximately 10-15% of MCDA twins.
Beginning at about 16 to 18 weeks of pregnancy, all MCDA twins undergo regular ultrasound surveillance for TTTS. If excess fluid (polyhydramnios) is noted for one twin and decreased fluid (oligohydramnios) is observed for the other, then a diagnosis of TTTS is confirmed and the health of the twins is further evaluated. While a range of options exist for the management of TTTS, contemporary therapy for early-onset, advanced-stage TTTS ideally involves fetoscopic laser therapy. Pregnancies complicated by TTTS require close surveillance even after therapy, and are at high risk for premature delivery.
TTTS is a disproportionately high contributor to death and disability among twin pregnancies around the time of childbirth. Outcomes for TTTS depend upon gestational age at diagnosis and severity, among other factors. Laser therapy has been shown to dramatically improve outcomes in these cases.