In intention-to-treat analysis , comparison of women who received iron vs placebo , respectively , yielded the following results at birth : Plasmodium infection risk : 50.9 % vs 52.1 % ( crude difference , -1.2 % , 95 % CI , -11.8 % to 9.5 % ; P = .83 ) ; birth weight : 3202 g vs 3053 g ( crude difference , 150 g , 95 % CI , 56 to 244 ; P = .002 ) ; birth-weight-for-gestational-age z score : 0.52 vs 0.31 ( crude difference , 0.21 , 95 % CI , -0.11 to 0.52 ; P = .20 ) ; and at 1 month after birth : maternal hemoglobin concentration : 12.89 g/dL vs 11.99 g/dL ( crude difference , 0.90 g/dL , 95 % CI , 0.61 to 1.19 ; P < .001 ) ; geometric mean maternal plasma ferritin concentration : 32.1 g/L vs 14.4 g/L ( crude difference , 123.4 % , 95 % CI , 85.5 % to 169.1 % ; P < .001 ) ; geometric mean neonatal plasma ferritin concentration : 163.0 g/L vs 138.7 g/L ( crude difference , 17.5 % , 95 % CI , 2.4 % to 34.8 % ; P = .02 ) .