Background: Micronutrient deficiencies, specially iron, render pregnant women as one of the most vulnerable groups to have anemia. Aim: To report the prevalence of anemia during pregnancy and its associated features in women attending public clinics in the Puente Alto County. Material and methods: We studied 1683 pregnant women aged 18 years old or more. Hemoglobin concentration was determined using the cianmetahemoglobin method. Anemia was defined using the 5th percentile cut-off for each week of gestational age as proposed by R Yip from the Centers of Disease Control, 1989. The influence of maternal age, parity, nutritional status classified using weight/height, diseases and smoking habits on hemoglobin concentration were analyzed using logistic regression with a stepwise procedure. Results: Thirteen percent of the study population was anemic. The single factor significantly associated with anemia was nutritional status. Twenty one percent of women with a low weight for height were anemic. Conclusions: These results support the concept that pregnant women with a low weight for height have the greatest risk for anemia and should be specially benefited with preventive or treatment programs to avoid this problem (Rev Méd Chile 2003; 131: 520-525).