Consanguinity and late fertility: spatial analysis reveals positive association patterns

The role of consanguinity on human complex traits is an important and controversial issue. In this work we focused on Sardinian population and examined the effect of consanguineous unions on late female fertility. During the last century the island has been characterized by high incidence of marriages between relatives, favoured by socio economic conditions and geographical isolation, and by high fertility despite a widespread tendency to delay reproduction. Through spatial analysis techniques, we explored the geographical heterogeneity of consanguinity and late fertility, and identified in Central-Eastern Sardinia a common excess area where the traits are positively associated. We found that their association did not significantly affect woman’s fertility in the area, despite the expected negative role of both traits. Intriguingly, such critical zone includes the genetically homogeneous Ogliastra region, and well matches areas reported by previous studies as peculiar for high frequency of centenarians and for lower risk in pregnancy outcome. The spatial analysis approach we adopted is quite general and can be exploited to single out critical areas where population screenings, carried out at molecular level, could help disentangle determinants of complex biological traits and investigate their association.