Iron deficiency during pregnancy affects a significant portion of women in countries with low economic wealth and is not uncommon in pregnant women in industrialized countries. Inadequate intake of iron related to diets poor in bioavailable iron is often responsible for iron deficiency before pregnancy, and metabolic adjustments (such as mobilization of iron stores and increased absorption) are insufficient to meet increasing needs during pregnancy. The effects of iron deficiency on the fetus are still controversial. Numerous measures, including the evaluation of erythrocyte ferritin, favor the hypothesis that the level of iron stores in newborns is related to maternal iron status and that the materno-fetal unit is dependent on exogenous iron, which is necessary to prevent iron deficiency in both mothers and infants. In industrialized countries, iron supplements should be prescribed for pregnant women in the third trimester, when the need for iron is prominent. In developing countries, supplementation should be initiated as soon as possible after conception because of the high prevalence of iron deficiency at the onset of pregnancy. The results of studies comparing intermittent with daily supplementation remain controversial.

Haematological and folic acid status were assessed in 200 women in the 6th month of pregnancy. Folic acid deficiencies with no or little haematological impairment were found in one third of the cases, and their occurrence increased when the socioeconomic level was low. During the last trimester of pregnancy, the women were given either iron alone or iron and folic acid supplementation. In the mothers, the rise of folate values in serum and red blood cells, in the folic acid-supplemented group, had no obvious haematological consequences, showing that iron therapy alone can, in developed countries, prevent the anaemia in pregnancy. In the infants, there was no difference in the haematological indices, whatever the mothers’ treatment had been. However, a significant difference appeared for the gestational age and, therefore, the height and weight. Folic acid supplementation during pregnancy increased its duration by virtually 1 week.

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Iron and folate status of 203 pregnant women have been evaluated at 6 months gestation and on the same women and their newborn infants at delivery. The women who had, at 6 months gestation, a Hb level below 11 g/dl were systematically given iron supplements. Iron or placebo were randomly allocated to the other women. At 6 months of pregnancy, one quarter of the women had a Hb level under 11 g/dl but one third had a serum ferritin level below 12 µg/l and more than half had low levels of serum and red cell folate. Iron supplements induced an increase both in Hb levels and in serum ferritin values; however, no significant differences were observed in serum ferritin of the newborn infants, whether their mothers had received iron supplements or not. These results have led us to reconsider the value of ferritin levels at birth as an index of iron stores in the infant. Iron supplements had no effect on the folate status in mothers or infants or on the frequency of obstetrical complications. A significant relationship was found between maternal folate levels and length of gestation. Folate supplementation may reduce the incidence of premature delivery.