Inbreeding effects on fertility and sterility: a case-control study in Saguenay-Lac-Saint-Jean (Québec, Canada) based on a population registry 1838-1971.
Effects of inbreeding on couples' fertility and primary sterility were investigated in five marriages between uncle and niece, 251 marriages between first-degree cousins, and 358 marriages between first-degree cousins once removed from Saguenay-Lac-Saint-Jean. Three control groups matched on the demographic and socioeconomic characteristics of the consanguineous couples were created. The number of children born to each couple was extracted from a computerized population registry. The level of primary sterility was found to be similar in all consanguineous and non-consanguineous groups. The mean number of children in all three consanguineous groups was not found to be significantly different from that calculated in their respective control groups (p > 0.05). These results are compatible with those obtained in virtually all the studies reported thus far in different populations.