Hydrops fetalis due to isoimmunization

This diagnosis code signifies a severe form of fetal anemia and generalized edema (hydrops fetalis) resulting from an immune response in the mother against fetal red blood cell antigens. This immune response, known as isoimmunization, leads to the destruction of fetal red blood cells, causing anemia and subsequent heart failure and fluid accumulation in multiple fetal compartments.

Use this code when documentation clearly indicates hydrops fetalis is caused by maternal alloimmunization, such as Rh incompatibility or other red blood cell antigen incompatibilities. This diagnosis is typically made antenatally via ultrasound findings of fetal edema and confirmed by serological testing of maternal and fetal blood.

• Always confirm the underlying cause of hydrops fetalis is isoimmunization; other causes (e.g., genetic, infectious) require different codes.
• Do not confuse with non-immune hydrops fetalis (P83.2), which has a different etiology.
• Sequence this code as the primary diagnosis when it is the main reason for the encounter or admission, followed by codes for specific maternal conditions if applicable.