RESUMO
ABO and Rho(D) blood groups were determined in 3813 males and females affiliated with the Instituto Mexicano del Seguro Social (IMSS) who are residents of the Monterrey Metropolitan Area (MMA) in northeastern Mexico. They were selected by their monophyletic or polyphyletic surnames. The ABO and Rho(D) blood group phenotypes and gene frequencies were determined and based upon these, the risk of incompatibilities was estimated for both marriages (MI) and maternal-fetal incompatibility (MFI). These were compared with those estimated for other populations of residents in the MMA, and in other locations in Mexico, as well as with the two most important ancestral populations, Spanish and Tlaxcaltecan Mexican Indians, with the hypothesis that the percent of risk ABO and Rho(D) MI and MFI are greater in the population with monophyletic surnames than those with polyphyletic surnames. It was found that for persons with nomophyletic and polyphyletic surnames, as well as for the other populations in the MMA and other places in Mexico, their ABO and Rho(D) MI and MFI percent of risk are intermediate to the ones estimated for their ancestry. The percentages of MI and MFI are higher for the persons with monophyletic than for the ones with polyphyletic surnames, other populations from the MMA and those from other locations in Mexico. The risks are higher when the similarity with Spanish increases and are lower when their similarities with the mexican Indians increase