[The critical hemoglobin/hematocrit value in obstetrics].

During pregnancy, there are characteristics changes in the hemoglobin and hematocrit values. Compared with the norm for nonpregnant women, there is an increase in the total number of erythrocytes and in the plasma volume. An overproportional increase of the latter results in hydremia. The normal physiologic range for hemoglobin during pregnancy is 11.5-13.0 (13.5) g/dl; anemia is, by definition, present when the values are under 11 g/dl and is quite common in pregnancy. Since it is caused almost exclusively (95%) by iron deficiency, iron therapy or routine iron supplementation can influence its incidence. Values outside the norm range are associated with complications during pregnancy and with growth retardation of the fetus.