The study of two birth cohorts in Pelotas (Southern Brazil) in the years 1982 and 1993 allowed for a comparison of maternal characteristics, including biological, socioeconomic, demographic, and reproductive variables. All women living in urban Pelotas and giving birth in the city maternity hospitals were interviewed with a structured questionnaire. There were 6,011 births in 1982 and 5,304 in 1993. Women in the 1993 cohort were of a higher socioeconomic status (as measured by familiy income and years of schooling). They were also significantly taller and heavier than mothers giving birth in 1982. Mean parity did not differ for the two groups, but in 1993 there were fewer primiparae and more women with four or more children. The birth interval was also significantly greater in 1993; one possible reason (in addition to more frequent use of contraceptives) was an increase in the number of previous abortions observed in 1993 as compared to 1982.