Biosocial perspective of consanguineous marriages in rural and urban Swat, Pakistan.

Consanguineous marriages in two population samples, one rural and one urban, from Swat (Pakistan) were studied. The frequency of consanguineous marriages was found to be 37.13% and 31.11%, and mean inbreeding coefficients were calculated as 0.0168 and 0.0162, for the rural and urban populations respectively. The most frequent type of marriage was between first cousins, in both samples. Among first cousin marriages, those with father's brother's daughter were predominant. Mean inbreeding coefficient was higher for higher socioeconomic groups in both samples. Differences by ethnic and educational groups were also found. Contrary to previous studies, a significant increase in the incidence of consanguineous marriages over the years has been observed. The incidence of premature mortality was significantly higher only in the offspring of first cousin marriages. Significantly higher incidence of morbidity in the offspring of consanguineous marriages was also observed.