Statistical analysis
anaemia, pre-delivery anaemia
ANAEMIA, SECONDARY, IRON DEFICIENCY ANAEMIA, IRON DEFICIENCY, REGRESSION
Sample size is based on the maternal primary outcome of proportion of women with pre-delivery anaemia (venous haemoglobin <11·0 g/dL). We estimated routine iron supplementation would reduce anaemia from 100% to 60%, on the basis of reductions in anaemia seen in cohorts of pregnant women treated with ironAnalysis followed a pre-specified statistical analysis plan.Maternal anaemia (primary outcome) was analysed using a mixed effects Poisson regression model. The model included fixed effects of treatment, study visit, and the treatment by study visit interaction, with a random intercept for the women and robust standard error. Similar analyses were applied to repeatedly measured dichotomous secondary maternal outcomes. Secondary maternal outcomes of Hb and log-transformed ferritin were analysed using a likelihood-based longitudinal data analysis model by Liang and Zeger,Results are presented as point estimates and two-sided 95% CIs. No multiplicity adjustment is applied to CIs, and these cannot be used in place of hypothesis testing. A two-sided p value <0·05 was used to indicate significance for the primary maternal outcome and the primary neonatal outcome. The Holm procedure was used to control family-wise error rate at 0·05 for the key secondary maternal outcomes at 36 weeks' gestation (haemoglobin concentration, moderate–severe anaemia, ferritin concentration, iron deficiency, and iron deficiency anaemia) and neonatal outcomes (gestation duration, birth length, composite adverse birth outcome at delivery, and infant growth at 4 weeks' post partum).