How rh issoimmunization cause polhydroamnios?

Rh isoimmunization can lead to polyhydramniOS due to the development of severe fetal anemia, which often results from hemolytic disease in the fetus. The anemia stimulates increased fetal erythropoiesis, leading to the production of excess fetal blood cells and increased fetal urine output, contributing to greater amniotic fluid production. Additionally, fetal heart failure, a potential consequence of severe anemia, can further exacerbate the condition by affecting fluid dynamics. As a result, the accumulation of excess amniotic fluid characterizes polyhydramniOS.