In a case of twin-twin transfusion syndrome, which type of anastomoses is likely causing the hematocrit disparity between the twins?

In twin-twin transfusion syndrome (TTTS), there is an unequal flow of blood between the twins, which leads to a significant difference in their hematocrit levels. This condition occurs primarily in cases of monochorionic twin pregnancies, where both twins share a single placenta.

The primary mechanism behind this hematocrit disparity is the presence of vascular anastomoses on the chorionic surface of the placenta. Specifically, artery-to-artery anastomoses play a key role in facilitating the unequal blood flow that characterizes TTTS. These anastomoses connect the arterial systems of both twins, allowing blood to flow from one twin (the donor) to the other (the recipient). This can result in the recipient twin having a higher hematocrit due to receiving excess blood, while the donor twin has a lower hematocrit due to losing blood.

Other options do not directly explain the hematocrit disparity. Amniotic fluid leaks typically relate to other complications in pregnancy but are not involved in the direct blood supply between twins. Chronic abruptio placentae refers to placental separation that can lead to various complications but also does not explain the transfusion dynamics. Funisitis involves inflammation of the umbilical cord, which