Male fertility patterns in Nigeria, South Africa, and Uganda: How many marital unions and children?

Men's marital trajectories are important for understanding fertility dynamics but have received limited attention in demographic research, particularly in sub-Saharan Africa. This study examined the association between the number of marital unions and the total number of biological children fathered among men in Nigeria, South Africa, and Uganda. A cross-sectional secondary analysis was conducted using harmonized IPUMS-DHS datasets from the three countries. The weighted sample consisted of 11,437 men aged 15–59 years. Descriptive statistics, and country-specific multivariable linear regression models were employed to examine the relationship between number of marital unions and fertility outcomes. Men in multiple marital unions fathered significantly more children than those in a single marital union in Nigeria (β = 1.55, 95% CI: 1.38–1.72) and Uganda (β = 1.04, 95% CI: 0.85–1.24), while no statistically significant association was observed in South Africa (β = 0.17, 95% CI: −0.14–0.48). Older age groups, rural residence, and higher ideal number of children were positively associated with fertility across the three countries. Conversely, higher education and later age at first marital union were associated with lower fertility. Working status, wealth index, contraceptive use, and exposure to family planning messages showed inconsistent associations across the countries. The findings demonstrated that number of marital unions played an important but context-specific role in shaping male fertility outcomes. Policies promoting delayed marital union formation, increased educational attainment, rural reproductive health access, and greater male involvement in family planning programmes are essential for fertility transition and control in the region.