[Incidence of Down syndrome at a University Hospital Maternity of Chile. A 25-year record: 1972-1997].

BACKGROUND

The main function of ECLAMC (Latin American Congenital Malformations Collaborative Study) is to monitor congenital malformations in Latin American countries. Down syndrome, due to its medical and social importance, has received special concern.

AIM

To measure the rates of incidence of Down syndrome in an University hospital maternity and to compare demographic variables of children born with the syndrome and healthy children.

MATERIAL AND METHODS

Between 1990 and 1997, all children born with Down syndrome were registered, and the next healthy newborn of the same sex was considered as control. Also, using previous registers, the prevalence of newborns with Down syndrome and the mean maternal age from 1972 to 1997 were compared using regression equations.

RESULTS

During the 7 years study period, 53 Down syndrome patients were born (66% female, two stillbirths). Thirty percent had congenital heart disease, forty seven had a regular 21 trisomy, one had a Robertsonian translocation, two had mosaicism for 21 trisomy, one was 48, XXX + 21 and one was 48, XXY + 21. Compared to controls, these children had lower gestational age and birth weight, mean maternal and paternal ages were higher, previous abortions were more frequent and the intergenesic period more prolonged. From 1972 to 1997, both the birth rate of Down syndrome and mean maternal age increased significantly with slopes of 0.13 years of age per year and 0.05/1000 born alive per year, respectively. Comparing both rates, the prevalence rate of Down syndrome increased in 0.31 per 1000 born alive per year of increment in maternal age. Father's age had no influence on this prevalence.

CONCLUSIONS

In the period 1990-1197, a higher prevalence rate of Down syndrome than in previous periods in the same maternity, was found. The influence of maternal age on this prevalence was clearly established.