Background: One of the aspects that helps to understand the genetic structure of a population throughout its biological history is the description of its matrimonial practices. Thus, the objective of this study is to explore consanguinity, one of these practices, to its full extent by identifying the prevalence, determinants, and trends of a consanguineous marriage, as well as its impact on fertility and spontaneous abortions in the Chaouia population, a region located in the western center of Morocco. Therefore, a survey-based cross-sectional study was conducted between January 2019 and January 2020. The sample was collected by province using a stratified random sampling approach, yielding a sample of 788 people. The association between consanguinity and socioeconomic and demographic characteristics, as well as reproductive health and pregnancy outcomes, was described using chi-square and ANOVA analysis. Multivariate logistic regression analysis was used to determine the predictors of a consanguineous marriage. Results: Our findings revealed a consanguinity rate of 25.38%. The mean inbreeding coefficient was 0.012214. The most common type of union was between first cousins. This practice was strongly associated with an early age at marriage for both genders and with endogamy and immobility of couples, according to their place of birth. Consanguinity was significantly associated with fertility (p < 0.001) and spontaneous abortions (p = 0.029). The average number of pregnancies and spontaneous abortions was higher in consanguineous unions (5.18 ± 0.20/0.47 ± 0.08) compared to non-consanguineous unions (4.33 ± 0.10/0.31 ± 0.03). Conclusions: Consanguinity is a deeply rooted social and cultural tradition in this population, providing individuals with a sense of social-economic stability while assuring their attachment to the group. Despite being highly associated with fertility, this practice has a significant influence on pregnancy outcomes, namely spontaneous abortions. Therefore, further studies are needed to examine the impact of consanguinity on various aspects of reproductive health and its association with numerous genetic abnormalities and diseases.