The aim of the present study was to measure the proportion of adolescent pregnancies in Montes Claros, Minas Gerais, Brazil. From a total of 7,672 live births in 2001, the estimated proportion of births by adolescent mothers was 21.5%. In addition to the limited presence of adequate frequency in prenatal visits, especially in the 10-14-year bracket (12.0%), the study identified an increase in the number of complications, inversely related to age, and these differences were significant in relation to prematurity and low birth weight, which did not occur with the 5-minute Apgar score. Confirming the hypothesis of greater frequency of these complications when the number of prenatal visits was inadequate, the outcomes also signal an age-associated risk, particularly in early adolescence (10-14 years). These results, together with the data on an increase in adolescent pregnancy in the region from 1997 to 2001, point to teenage pregnancy as a public health problem.