Experimental plan: Pregnant women are included during the ultrasound of T1. Written consent will be sought after delivery of the information notice. Hemoglobin, classical iron balance (ferritin, transferrin saturation coefficient) as well as other original parameters: hepcidin and the soluble transferrin receptor are assayed. Socioeconomic and clinical parameters likely to favor an iron deficiency are sought through validated questionnaires. Nutritional advice, combined with martial supplementation if necessary, is given according to a standardized management protocol resulting from the current international recommendations and validated by an internal committee. The prevalence of iron deficiency anemia is determined at T3 (after 34 SA). The predictive factors for this anemia will be sought according to the data collected in T1.