Several anthropometric patterns were used to evaluate the nutritional status of 155 pregnant teenagers of low socioeconomic status in a prenatal care unit of a beneficent hospital in São Paulo, Brazil. Using the body mass index 25.2% of them were classified as underweight before pregnancy and 3.3% during pregnancy. The Siqueira's et al curve and the Rosso's normogram showed higher percentages of underweight, as well as of overweight and obesity. The results indicated the necessity to review the anthropometrics patterns that classify specifically the nutritional status of pregnant adolescents.