Daily iron supplementation does not impact on prevalence of exclusive breastfeeding or growth in young breastfed Gambian infants

Background In a randomised placebo-controlled trial among exclusively breastfed rural Gambian infants aged 6–10 weeks at randomisation, daily iron supplementation for 14 weeks improved iron status. This secondary analysis explores the impact of iron supplementation on duration of exclusive breastfeeding and growth. Methods Breastfed 6–10 week-old infants were supplemented for 14 weeks with either daily iron or placebo (n=101). Infant feeding practices were assessed weekly through questionnaires. Survival analysis was used to measure the effect of iron supplementation on age at and time to cessation of exclusive breastfeeding. Groups were also compared regarding the change in anthropometric z-scores between baseline and endline. Results At endline, 31% (n=31/101) of infants were exclusively breastfed. There was no evidence that iron supplementation reduced the time to cessation of exclusive breastfeeding (median: 70 days (range: 7–105 days), iron: 67 days; placebo 71 days; Kaplan-Meier, log-rank test: p=0.15; Cox regression, crude HR: 1.42, 95% CI: 0.86 to 2.34, p=0.17; HR adjusting for infant age and sex: 1.40, 95% CI: 0.85 to 2.31, p=0.19) or age at cessation of exclusive breastfeeding (median time: 18 weeks (range:1–24 weeks), iron: 16 weeks; placebo 18 weeks; Kaplan-Meier, log-rank test: p=0.13; crude HR=1.47, 95% CI: 0.89, 2.43; p=0.13; HR adjusting for infant age and sex=1.44, 95% CI: 0.87, 2.39 p=0.16) There was no evidence that iron supplementation affected infant weight (p=0.79) or length (p=0.64) at endline or change in z-scores during the intervention period for weight-for-age (p=0.99), length-for-age (p=0.70) and weight-for-length (p=0.89). There was no evidence that duration of exclusive breastfeeding impacted endline anthropometric outcomes. Conclusion Although requiring replication in larger trials, these findings do not raise concerns about iron supplementations’ effect on feeding or growth in exclusively breastfed infants.