Table 2.

Associations of customised birth weight centile with indicators of iron status during pregnancy in the Baby's Vascular health and Iron in Pregnancy study (Differences and 95 % confidence intervals)

	Difference in birth weight centile mean*
Predictor	Unadjusted difference	95 % CI for unadjusted difference	P	Adjusted difference†	95 % CI for adjusted difference	P	n (multivariable model)
Maternal sF at 12 weeks gestation (per 10 μg/l change)	− 0·1	− 1·0, 0·6	0·9	0·1	− 0·6, 0·7	0·9	341
Maternal Fe depletion at 12 weeks gestation (sF < 15 μg/l)	− 4·2	− 11·3, 2·3	0·3	− 4·6	− 11·7, 2·5	0·2	341
Maternal sTfR at 12 weeks gestation (per nmol/l)	− 0·2	− 0·7, 0·4	0·5	− 0·3	− 0·8, 0·3	0·3	341
Maternal log sTfR:sF ratio at 12 weeks gestation (per μg/l)	− 0·8	− 3·4, 1·7	0·5	− 1·2	− 3·8, 1·3	0·3	341
Maternal Hb at ≤ 20 weeks gestation (per 10 g/l)	1·4	− 1·7, 4·5	0·4	1·0	− 2·0, 4·1	0·6	326
Maternal Hb at >20 weeks gestation (per 10 g/l)	− 0·8	− 3·7, 2·2	0·6	− 1·2	− 4·4, 1·4	0·3	334
Maternal anaemia at ≤ 20 weeks gestation ( < 110 g/l)	− 15·0	− 29·2, − 1·0	0·04	− 11·2	− 25·4, 3·1	0·1	326
Maternal anaemia at >20 weeks gestation ( < 105 g/l)	− 4·5	− 13·1, 4·2	0·3	− 1·4	− 10·1, 7·3	0·8	334

sF, serum ferritin; sTfR, serum transferrin receptor.

^*Customised birth weight centile (takes into account maternal pre-pregnancy weight, height, ethnicity, parity, gestational age and baby's sex).

^†Adjusted for maternal age, smoking, gestational diabetes, pre-eclampsia and area deprivation score (Index of Multiple Deprivation).