No increased histocompatibility antigen-sharing in couples with idiopathic habitual abortions.

Sharing of major histocompatibility antigens between spouses has been claimed to play an aetiological role in couples with unexplained, habitual spontaneous abortions. On the other hand there is evidence that a subset of habitually aborting women exists, in whom autoimmune aberrations seem to be of importance. In the present study, 56 couples with unexplained habitual abortions were histocompatibility typed for HLA-A, -B and -DR specificities, as were a group of 33 fertile control couples with two or more children and no spontaneous abortions. The DR-typing was done partly by use of the restriction fragment length polymorphism (RFLP). There was no significant difference in the distribution of histocompatibility antigens between the habitually aborting women and the control women. No increased HLA-antigen sharing could be demonstrated between spouses in aborting couples compared with controls, neither in each single locus nor in the combination of all loci (all P-values greater than 0.2). Neither could any increased HLA-antigen sharing in sub-groups of aborting couples with and without autoimmunity be demonstrated. It can be concluded from these data that compatibility between spouses for HLA-A, -B and DR-antigens per se only plays a minor role in the aetiology of habitual abortion.