Is a 24-Month Birth Interval Enough? Evidence from a cross-sectional study using the Benin Demographic and Health Survey

Background: Stunting affects approximately 32% of children under five years in Benin. While birth intervals shorter than 33 months are a recognized risk factor for childhood malnutrition, the optimal birth interval for preventing stunting in the Beninese context is still unclear. Objective: This study examined the association between preceding birth interval (PBI) and stunting among children aged 6 to 59 months in Benin. Methods: This study used a cross sectional design to analyze data from the 2017 to 2018 Benin Demographic and Health Survey. We included 10,153 children aged 6 to 59 months. Stunting was defined as height for age z score below 2 standard deviations from World Health Organization standards. Preceding birth interval was categorized as <24, 24 to 32, 33 to 44, 45 to 56, and >56 months. Survey adjusted multivariable logistic regression was used to estimate adjusted odds ratios (aORs) and 95% confidence intervals for the association between PBI and stunting, controlling for child, maternal, and household level covariates. Potential effect modification by child age group (6 to 23 vs. 24 to 59 months) was assessed through a multiplicative interaction term and evaluated using information criteria, a likelihood ratio test, and the statistical significance of individual interaction terms. Results: Compared with children born after an interval of <24 months, those born after 45 to 56 months (AOR: 0.63; 95% CI: 0.51 to 0.78) and >56 months (AOR: 0.67; 95% CI: 0.54 to 0.82) had significantly lower odds of stunting (both p<0.001). Intervals of 24 to 32 months and 33 to 44 months were not significantly associated with stunting, nor was firstborn status. No evidence of effect modification by child age group was found (likelihood ratio test p=0.336), and stratified analyses conducted separately for children aged 6 to 23 months and 24 to 59 months yielded results consistent with those from the pooled model. Conclusion: The lack of protective effect for intervals shorter than 45 months indicates a threshold specific to this context above which nutritional benefits become manifest. Integrating family planning messages emphasizing birth intervals longer than 45 months into child nutrition programs, coupled with strengthened access to modern contraception, could contribute to stunting reduction in Benin among other factors. Alongside this, nutritional support for pregnant and breastfeeding women, including adequate dietary supplementation and counselling, may further contribute to improved child growth outcomes. Keywords: Birth interval; stunting; family planning; Benin; childhood morbidity; nutrition