[Increasing rates of Down syndrome among newborns in Chile from 1972 to 2005].

Background: There are some records shrowing that the frequency of Down syndrome is experiencing an increase over time.

Aim: To verify whether the frequency of Down syndrome is increasing in the maternity of the University of Chile Clinical Hospital, or in other Chilean hospitals participating in the Latin American Collaborative Study of Congenital Malformations (ECLAMC) and compare the rates with other world registries of congenital malformations.

Material And Methods: The information was obtained from the ECLAMC databases of the maternity. The Down syndrome incidence rates were calculated from 1997 to 2005 and rate curves were constructed.

Results: The overall rate of Down syndrome was 3.36 per 10,000 born alive. This rate experienced a significant increase in the study period. These rates differ in the different Chilean regions, being higher in Santiago and lower in the Southern regions of the country. The mean age of mothers of newborns with or without Down syndrome was 36+/-6 and 29+/-6 years, respectively, p >0.001.

Conclusions: The rates of newborns with Down syndrome increased in the period 1972-2005, bearing a close relationship with the increase in maternal ages.