Résumé
Background: Chile is in the advanced stage of demographic transition with a low natural growth and a progressively aging population. Aim: To analyze births by range of maternal age and to establish if population aging is expressed in the women's fertile age range. Material and methods: Trend analysis of births and age-specific birth rates in the period 1990-2004, in the Chilean women population of reproductive age. Raw data were obtained from the Vital Statistics Yearbooks of the National Institute of Statistics. Trends were studied by linear regression and Generalized Estimating Equation (GEE). Results: The general trend of births descended significantly from 1999 to 2004 (r: -0.996; p <0.001). Births significantly decreased in the range of ages from 20 to 34 years. There was an increase in the range of ages from 35 to 44 and from 10 to 14 years. The age-specific birth rate declined in all ranges, with the exception of women aged 10 to 14 years. The number of women increased significantly at all age ranges, except for the 20-24 year-old range where no significant change was observed and the 25-29 year-old range that experienced a significant reduction. Conclusions: In the period from 1990 to 2004, there was a significant reduction of births and age-specific birth rates in Chile. There was also an increased birth rate among women aged 35 to 44 years and an aging of the fertile women population.