Objectives. Determine hemoglobin levels and prevalence of anemia in pregnant women seen in health care centers of the Ministry of Health at national level. Materials and methods. Cross-cut study where the database of the Information System on the Nutritional Health of Children under 5 and Pregnant Women (SIEN) were analyzed. 287 691 records of pregnant women examined at the health care centers of the Peruvian Ministry of Health in 2011 were included, hemoglobin levels corrected by height, age, gestational age, altitude and prevalence of anemia (light, moderate and serious) were analyzed. Descriptive statistics and the chi-square method were used. Results. Nationwide prevalence of anemia in pregnant women was 28.0%, with mild anemia being at 25.1%, moderate anemia at 2.6% and severe anemia at 0.2%. Hemoglobin levels are higher in older and younger women during the first months of pregnancy, prevalence of anemia decreases with altitude. Furthermore, prevalence is higher in the Highland regions. Huancavelica was the region with higher prevalence of anemia (53.6%), followed by Puno with 51.0%. Conclusions. Hemoglobin levels get higher as the mother gets older, and they go down in keeping with the gestation trimester and altitude. Huancavelica has the highest prevalence of anemia in pregnant women.