Insufficient saturation of the organism with iron, and subsequent anemia can occur in particular during pregnancy. According to the results of some trials more than 50% of women have inadequate supply of iron and iron deficiency anemia may have about 15% of women. In non-pregnant women higher blood loss during menstruation decreases iron supply. The clinical consequences of iron deficiency anemia can lead to premature birth, perinatal and postpartum depression. The consequences for the fetus and neonate include low birth weight and poorer mental and psychomotor performance. Oral medication is usually sufficient treat the iron deficiency. Treatment should be initiated at the drop of ferritin < 12 mg/l and transferrin saturation < 20%. The length of supplementation is individual, but it usually takes weeks, sometimes months. Women who are taking daily iron supplementation during pregnancy have 1. lower risk of anemia during birth, 2. higher hemoglobin levels as during deliver and postpartum period. Those who took the higher dose, had higher levels of Hb. 3. have a higher probability of elevated levels of Hb in the second and third trimesters of pregnancy. 4. have a slightly lower risk of delivering a baby with low birth weight and birth before 37. weeks. 5. have a lower risk of preterm birth before 34. weeks of pregnancy.