Even with treatment, the condition is associated with premature birth and a risk of cerebral palsy in a surviving fetus. Around 5–15% of identical twin fetuses will go on to develop TTTS. The condition was first described by German obstetrician Friedrich Schatz in 1875. Cause
As a result of sharing a single placenta, the blood supplies of monochorionic twin fetuses can become connected, so that they share blood circulation: although each fetus uses its own portion of the placenta, the connecting blood vessels within the placenta allow blood to pass from one twin to the other. It is thought that most monochorionic placentae have these "shared connections" that cross the placenta, with the net flow volumes being equal between them. This state is sometimes referred to as "flow balance". When the placenta has deep vein–artery connection, this can cause blood flow to become unbalanced.Depending on the number, type and direction of the interconnecting blood vessels (anastomoses), blood can be transferred disproportionately from one twin (the "donor") to the other (the "recipient"), due to a state of "flow imbalance" imparted by new blood vessel growth across the placental "equator", the line that divides each babys proportion of the shared placenta. This state of transfusion causes the donor twin to have decreased blood volume, retarding the donors development and growth, and also decreased urinary output, leading to a lower than normal level of amniotic fluid (becoming oligohydramnios).
The spontaneous form of TAPS complicates approximately 3 to 5% of monochorionic twin pregnancies, whereas the post-laser form occurs in 2 to 13% of TTTS cases. The pathogenesis of TAPS is based on the presence of few, minuscule arterio-venous (AV) placental anastomoses (diameter <1mm) allowing a slow transfusion of blood from the donor to the recipient and leading gradually to highly discordant Hb levels.A 2014 review found that laser coagulation resulted in fewer fetal and perinatal deaths than amnioreduction and septostomy, and recommended its use for all states of TTTS. Umbilical cord occlusion
This procedure involves the ligation or otherwise occlusion of the umbilical cord to interrupt the exchange of blood between the fetuses. The procedure is typically offered in cases where one of the fetuses is presumed moribund and endangering the life or health of the other twin through resultant hypotension. Use of this treatment has decreased as TTTS is identified and treated in earlier stages and with better outcomes. When used, it is associated with an 85% survival rate of the remaining fetuses with 5% risk of cerebral palsy and a 33–39 weeks of gestation at delivery. Diet supplementation
Some doctors recommend complete bed rest for the mother coupled with massive intakes of protein as a therapy to try to counteract the syndrome. Research completed shows these nutritional supplements do work.Diet supplementation was associated with lower overall incidence of TTTS (20/52 versus 8/51, P = 0.02) and lower prevalence of TTTS at delivery (18/52 versus 6/51, P = 0.012) when compared with no supplementation.