Approximately one third of the 5.5 billion people in the world are anemic. Worldwide, approximately 40% of children (0–12 years), 35% of all women, 51% of pregnant women, and 18% of men are anemic.<sup>17 DeMaeyer E.M., Adiels-Tegman M. The prevalence of anaemia in the world World Health Stat Q 1985 ;  38 : 302

Haga clic aquí para ir a la sección de Referencias</sup> These figures are probably conservative estimates because the diagnosis of anemia is based on the World Health Organization definition of anemia: hemoglobin less than 11 g/dL for children aged 0 to 4 years and pregnant women, hemoglobin less than 12 g/dL for children aged 5 to 12 years and nonpregnant women, and hemoglobin less than 13 g/dL for men.<sup>51 Iron deficiency anemia Report of a study group. World Health Organ Tech Rep Ser No. 182, 1959

Haga clic aquí para ir a la sección de Referencias</sup> These values encompass worldwide populations and include developed and developing nations (Table 1). As might be expected, the prevalence of anemia is influenced by socioeconomic and geographic factors (e.g., poverty, marginal or famine diets, pregnancy rates, prevalence of malaria and hemoglobinopathies).

The magnitude of the problem in developing countries is enormous, especially among women and young children. Developed countries are also affected. Data for the United States in 1995 based on household interviews indicated that approximately 3% of women and 0.5% of men were anemic.<sup>49 Benson V., Marano M.A. Current estimates from the National Health Interview Survey 1995 Vital and Health Stat 10 1998 ;  199 : 80 82.

Haga clic aquí para ir a la sección de Referencias</sup> Percentages from the Mayo Clinic (1985–1987) for residents of Olmsted County, Minnesota, are somewhat higher, 6.6% in men and 12.4% in women.<sup>3 Ania B.J., Suman V.J., Fairbanks V.F. , y al. Prevalence of anemia in medical practice: Community versus referral patients Mayo Clin Proc 1994 ;  69 : 730

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Anemia is not a disease but evidence of an underlying condition, some of which are common and others rare or very rare. Worldwide, the most common conditions causing anemia are iron deficiency, thalassemia and hemoglobinopathies, folate deficiency, and parasitic diseases (especially malaria and hookworm infections and schistosomiasis).<sup>18 Fleming A.F. Anemia in pregnancy in tropical Africa Trans R Soc Trop Med Hyg 1989 ;  83 : 441  [cross-ref]

Haga clic aquí para ir a la sección de Referencias</sup> In the United States, there are three major causes—iron deficiency and thalassemia, each accounting for over one third of anemias, and the anemia of chronic disease, accounting for one fifth of anemias.<sup>6 Beutler E. The common anemias JAMA 1988 ;  259 : 2433

Haga clic aquí para ir a la sección de Referencias</sup> Folic acid and vitamin B₁₂ deficiency cause a small but important percentage. The remaining anemias are caused by various hematologic disorders, largely, the hemoglobinopathies and diseases with bone marrow failure. This article focuses on the common anemias in women that are seen in obstetrics/gynecology, family practice, and internal medicine. Anemia in infants and children is addressed only marginally when it relates to anemia in the mother. The anemia of chronic disease is not addressed because it occurs in both sexes without regard to gender.

Except for the anemia secondary to acute blood loss, anemia develops gradually and is asymptomatic until severe. Most anemias are picked up incidentally when blood counts are obtained for some other reason or as part of a screening work-up. The main function of the red blood cell is the delivery of oxygen to the tissues throughout the body in sufficient quantity to support their normal functions. The hemoglobin content of red blood cells must be capable of oxygen loading and unloading, and cardiopulmonary function must be adequate. Adaptation to a reduction in hemoglobin and, hence, in the delivery of oxygen occurs in the red blood cells and the cardiopulmonary system. Within the red blood cells, there is an increase in 2,3-diphosphoglycerate, a normal product of glucose metabolism in the cell. When bound to the hemoglobin molecule, this substance decreases its affinity for oxygen, leading to increased release of oxygen at the capillary level. As the anemia increases in severity, this mechanism alone is insufficient, and changes in cardiac function occur. Cardiac output is increased by increases in stroke volume and heart rate. There is peripheral vasodilatation, widening of the pulse pressure, shortening of circulation time, and shunting of blood from less vital to more vital structures. A normal heart can tolerate the additional work that these adaptations require. As the anemia worsens, the compensatory mechanisms become inadequate, and the patient experiences fatigue, palpitations, and shortness of breath with exertion or febrile illness. By the time hemoglobin levels decrease to 7 to 8 g/dL, symptoms can occur at rest or with minimal activity. At a level of 5 g/dL, activity is limited, and additional nonspecific symptoms can occur, such as low-grade fever, headaches, insomnia, loss of appetite, nausea, diarrhea, constipation, menstrual irregularities, and polyuria. The patient may complain of “hearing her heart beat in her ears.” In extreme anemia, high-output cardiac failure occurs even in young individuals with normal hearts. In the elderly, who are more likely to have coronary artery disease and some reduction in cardiac function, significant symptoms of heart failure can occur with much lesser degrees of anemia.

The evaluation of a patient with anemia begins with a careful and detailed history regarding blood loss, chemical and drug exposure, diet, family history, and anything that might suggest an underlying condition. There are no specific physical findings in mild anemia. Pallor of mucous membranes is rarely apparent. Skin and nail bed pallor is even less helpful because skin color varies widely among individuals, regardless of race. Cardiovascular examination will reflect the compensatory adjustment of the heart, that is, tachycardia, hyperdynamic precordium, widened pulse pressure, and evidence of heart failure. An assortment of murmurs may be heard that are caused by the rapid flow of less viscous blood and should not be ascribed to valvular abnormalities unless they persist after the anemia is corrected. Most important when performing the physical examination is a deliberate search for clues to an underlying disease that may be the cause of the anemia, such as evidence of weight loss, sites of chronic infection, petechiae, enlarged lymph nodes, abdominal organomegaly, or masses. Physical findings specific to the common anemias are described in the following sections.