ABO Incompatibility and Reproductive Failure among the Punjabis (Khatris and Aroras) of Delhi and Shimla

Abstract

Maternal–foetal ABO incompatibility is a common haematological problem affecting the newborn. In general, haemolysis is minimal and the clinical course is relatively benign, rarely causing escalating levels of hyperbilirubinaemia and significant anaemia commonly associated with the Rh haemolytic disease of the newborn (HDN). The hypothesis that ABO blood systems behave like the HLA system in relation to mother-conception tolerance-rejection mechanisms was tested in 983 mother–infant pairs. According to this hypothesis, heterozygotes carrying a paternal gene that is not present in their mother should be better tolerated than homozygotes. Significantly more BO infants born to AO mothers, AO infants born to BO mothers, and less significantly AO infants born to OO mothers confirm the hypothesis. These data strongly support the hypothesis that at least two foeto–maternal systems influence the destiny of pregnancies: the classical known incompatibility system, which operates late in pregnancy, and a new one, which is based on the induction of maternal tolerance early in pregnancy: maternal tolerance seems to be better elicited by heterozygous eggs or embryos carrying a gene not present in the mother. The data also support the hypothesis that sex ratio is influenced by foeto–maternal tolerance-rejection mechanisms associated with the ABO system.