Background: Consanguinity of human populations can but does not have to be associated with increased fertility. A recent study involving communities of Northeast Brazil revealed increased levels of endogamy.
Subjects and methods: Data from 20 451 interviewed couples and their 74 289 children were analysed.
Aim: The present study aimed to compare fertility between consanguineous and unrelated couples of these communities.
Results: Consanguineous and unrelated couples of the 39 communities had an average of 4.3 (SD = 0.9) and 3.5 (SD = 0.8) children (p < 0.0001), respectively. Average offspring number of consanguineous couples varied from 3.9 (SD = 1.1) to 5.6 (SD = 3.4) for couples related at the level of third cousins and double first cousin/uncle-niece, respectively (p < 0.005). The correlation coefficient between Human Development Index and fertility was -0.38 (p = 0.0179) and -0.23 (p = 0.17) for unrelated and related couples, respectively.
Conclusion: Results indicated an overall positive association between consanguinity and fertility. Fertility tended to be increased, for closely related couples, compared to those related more distantly.