Haemoglobin and serum ferritin in pregnancy—correlation with smoking and body mass index

Abstract Background Little is known about factors which may influence haemoglobin (Hb) and ferritin levels in pregnancy. Aim To analyse if haemoglobin and ferritin levels during pregnancy are influenced by maternal age, body mass index, cigarette smoking, and iron supplementation. Methods A random sample of 561 parous pregnant women were recruited from the catchment areas of three Scandinavian university hospitals. The analyses were based on 5024 haemoglobin and 1529 ferritin measures sampled from the first trimester to 42 weeks of gestation. Multilevel modelling was used to construct mean and percentile curves for haemoglobin and ferritin by gestational age. Results Women aged 25–34 years had significantly higher haemoglobin values than older and younger women. Haemoglobin values were significantly lower for women with body mass index 2 than for women with body mass index ≥19. Smokers had significantly lower haemoglobin values throughout pregnancy compared to non-smokers, with the lowest values among women who smoked 1–9 cigarettes per day. There were no similar associations between ferritin and maternal age, body mass index, or smoking. Women with iron supplementation throughout pregnancy had a higher relative increase in haemoglobin concentration toward the end of pregnancy. In non-supplemented women the decline in ferritin concentration was significantly steeper than in those who received iron supplementation. Conclusions Haemoglobin levels during pregnancy are significantly associated with maternal age, cigarette smoking, body mass index, and iron supplementation. No such associations were found with ferritin levels, except for iron supplementation.