Hydrops fetalis due to isoimmunization

**Definition:** A fetal condition characterised by an accumulation of fluid or oedema in at least two fetal compartments, including subcutaneous compartments, the pleura, the pericardium, or the abdomen, due to the transmission of IgG antibodies against the Rhesus factor of blood from the mother to the child via the placenta that break-down of the red blood cells of the fetus.