Answer:
Rh-negative
Step-by-step explanation:
Erythroblastosis fetalis is a clinical condition whereby maternal antibodies begin to attack the fetal red blood cells due to incompatibility in the Rh of mother and fetus. Rh, which stands for Rhesus factor, can either be positive (Rh+) or negative (Rh-).
However, this condition (erythroblastosis fetalis) occurs in mothers/women who are Rh-negative. When an Rh- mother carries a fetus that is Rh+, the antibodies in the white blood cells of the mother identifies the blood cells of the fetus as FOREIGN, hence, begin to attack it.
However, one preventive measure is that pregnant women who are Rh-NEGATIVE must be treated with injections called Rh immunoglobulin to prevent their antibodies from attacking their baby's red blood cells.