Considering that young women have a high risk of iron store deficiency, the iron supplementation is largely proposed during pregnancy. However, a selective supplementation reserved to anaemia women, must be preferred to a systematic supplementation which improves biological parameters of mothers but have no effect on newborns. Iron is a potentially toxic element and a not justified, supplementation could expose to high iron level and to an oxidative stress which is also observed in pregnancy pathologies (preeclamptia, gestational diabetes). Furthermore a non controlled increase of erythrocyte mass by iron supplementation could also alter the placenta exchange. As a precaution, iron supplementation may be reserved to anaemia women or with high anaemia risk. For others, nutritional advises must permit to reach iron recommendation.