Major histocompatibility antigens and spontaneous abortion: an evolutionary perspective.

Maternal-fetal histocompatibility as a consequence of sharing of MHC antigens between males and females may result in an increased incidence of spontaneous abortion. We propose that such a response may be of evolutionary significance in inbred populations where partners that are similar at MHC loci also are likely to share deleterious recessive alleles due to common descent. In this scenario, spontaneous abortion is regarded as an adaptive response on behalf of the mother, who terminates at an early stage her investment in an offspring which would likely be of low reproductive value if carried to term.