A study measured the concentrations of angiogenic and anti-angiogenic factors and showed that twin pregnant women with TTTS had higher levels of Endoglin and VEGFR-1 compared to those without TTTS while the placental growth factor (PlGF) levels were lower in the group with TTTS compared to those without TTTS 24. The gene discussed is ENG; the disease is twin to twin transfusion syndrome.