Isoimmunization is: Development of specific antibody directed at the red blood cells of another individual, such as a baby in utero. Often occurs when an Ph-negative woman carries an Ph-positive baby or is given Rh-positive blood.

Rh is the Rh factor, it is an inherited blood group on red blood cells like the ABO blood types. About 85% of the people in this country have it. Those who have it are "Rh-positive," those who don’t are "Rh-negative."In Arabic, it's known as an abbreviation for عامل الرايزيس

Rh-isoimmunization is a pregnancy symptom ocuuring when Rh -factor antibodies cross the placenta and affect the red blood cells of the fetus, causing anemia and other problems.

Accordingly, I'd suggest فقر دم الجنين or فقر الدم الناشئ عن تعارض عامل الرايزس