Abstract: A kit for testing materno-fetal immunoincompatibility in women, particularly in women whose fetuses are in danger, comprises two containers containing an identical amoung of HLA-D antigen-containing material and one container containing male serum as control. In the test, maternal serum of the patient is added to one container of antigen while the control serum is mixed with the other container of antigen. The amount of expressed HLA-D antigen remaining in each case is established by conventional HLA-D directed monoclonal antibody immunoassay techniques such as conventional radio-immunoassay. The maternal serum assay divided by the control serum assay gives an immunoincompatibility quotient (IQ). The IQ is from 40 to 50% in healthy pregnant women and is about 70% in pathological cases. The test provides reliable results since the antigenic portion is non-living and therefore does not offer the inconstances of living test reagents.