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 6-59 months in Benin.

Methods

This study used a cross-sectional design to analyze data from the 2017-18 Benin Demographic and Health Survey. We included 10,153 children aged 6-59 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, 24-32, 33-44, 45-56, 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 (6–23 vs. 24–59 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 45–56 months (AOR: 0.63; 95%CI: 0.51–0.78) and >56 months (AOR: 0.67; 95%CI: 0.54–0.82) had significantly lower odds of stunting (both p<0.001). Intervals of 24–32 months and 33–44 months were not significantly associated with stunting, nor was first-born 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 6–23 months and 24–59 months yielded results consistent with those from the pooled model.

Conclusion

The lack of protective effect for intervals shorter than 45 months indicates a context-specific threshold 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

STRENGTHS AND LIMITATIONS OF THIS STUDY

• This study draws on a nationally representative, large-sample dataset (n = 10,153 children aged 6–59 months) collected using internationally standardised methods, ensuring data reliability and generalisability.

• Analyses were adjusted for a comprehensive set of confounders at the child, maternal, and household levels, and stratified by age group (6–23 vs. 24–59 months) to capture age-specific patterns in the association between birth interval and stunting.

• Residual confounding from unmeasured determinants of stunting — including breastfeeding exclusivity, dietary diversity, recurrent infections, and genetic factors — cannot be ruled out despite adjustment for available proxy indicators.

• The data predate recent contextual changes in Benin (e.g., expanded social protection, COVID-19 pandemic, climate-related food insecurity), which may limit the contemporaneous applicability of the findings.