Background Despite the integration of iron supplementation into routine antenatal care programs as a nutritional intervention to prevent anemia in pregnant women, the use of this supplement for the recommended duration remains low in sub-Saharan Africa (SSA). Evidence on maternal compliance with iron supplementation at the SSA level is lacking and most of the previous studies have been limited to specific geographic areas. Therefore, the current study used large population survey data from 35 SSA countries to estimate the pooled prevalence of non-adherence and its determinants.

Methods A secondary analysis was conducted using data from the demographic and health surveys across 35 SSA countries. After excluding women with missing data on the outcome variable, a weighted sample of 158,941 women who received iron supplementation during their recent pregnancy was included in the analysis. Forest plot was used to present the pooled and country-level rates of non-adherence to antenatal iron supplementation. A multilevel mixed-effects Poisson regression with robust variance was done to identify determinants of non-adherence.

Results The pooled prevalence of non-compliance to iron supplementation in SSA was 65.1% [95% CI: 64.9 − 65.3%], with the lowest level in Zambia (18%) and the highest in Burundi (97%). The analysis revealed that living in rural areas (aPR: 1.16, 95% CI: 1.13–1.19), lack of access to mass media (aPR: 1.10, 95% CI: 1.09–1.12), low household wealth (aPR: 1.11, 95% CI: 1.09–1.14), late (aPR: 1.19, 95% CI: 1.17–1.20) and frequent ANC visit (aPR: 1.28, 95% CI: 1.26, 1.29), women’s employment status (aPR: 1.05, 95% CI: 1.03–1.06), husband illiteracy (aPR: 1.12, 95% CI: 1.10–1.13), and distance to a health facilities (aPR: 1.03, 95% CI: 1.01–1.05) were associated higher prevalence of non-adherence. Conversely, older maternal age was associated lower prevalence of non-compliance (aPR: 0.96, 95% CI: 0.94–0.97).

Conclusion More than six out of ten pregnant women in SSA do not take iron supplements for the recommended period, with substantial variations across the countries. The level of non-adherence was significantly varied by women’s sociodemographic and reproductive characteristics. This urges the need for strengthening community health interventions and other existing programs to reach women in rural and economically disadvantaged settings. Furthermore, promoting antenatal care services through mass media and community-based health education strategies is key for scaling up the utilization of the supplement. Our results also suggest the importance of establishing the community-based distribution of iron supplements to address women with limited access to the healthcare system.