[High prevalence of Down syndrome in the Rancagua Hospital in central Chile]. / Alta prevalencia de síndrome de Down en el Hospital Regional Rancagua, Chile. Período 1997-2003.

BACKGROUND: The Latin American Collaborative Study for Congenital Malformations (ECLAMC) has detected a higher incidence of Down syndrome in a zone of central Chile than in the rest of the country. AIM: To analyze the incidence rates of Down syndrome between 1997 and 2003 at the Regional Hospital of Rancagua, located 90 km south of Santiago, Chile. MATERIAL AND METHODS: The information obtained by ECLAMC was used. This program, using a case control methodology, registers all newborns with congenital malformations and assigns, as a control, the next normal newborn of the same sex. RESULTS: During the study period, 106 newborns with Down syndrome were registered, with a mean rate of 29.61 per 10,000 live births, twice higher than expected. The rate variations along the years of study suggest a cyclic change, with a hemicycle of six years. CONCLUSIONS: In this hospital, mothers under 35 years of age, have twice the risk of having a child with Down syndrome, than in the rest of the country.

Reduction of birth prevalence rates of neural tube defects after folic acid fortification in Chile.

To verify whether the decreasing neural tube defects birth prevalence rates in Chile are due to folic acid fortification or to pre-existing decreasing trends, we performed a population survey using a network of Estudio Colaborativo Latino Americano de Malformaciones Congenitas (ECLAMC, Latin American Collaborative Study of Congenital Malformations) maternity hospitals in Chile, between the years 1982 and 2002. Within each maternity hospital, birth prevalence rates of spina bifida and anencephaly were calculated from two pre-fortification periods (1982-1989 and 1990-2000), and from one fortified period (2001-2002). There was no historical trend for spina bifida birth prevalence rates before folic acid fortification, and there was a 51% (minimum 27%, maximum 66%) decrease in the birth prevalence rates of this anomaly in the fortified period. The relative risks of spina bifida were homogeneous among hospitals in the two period comparisons. There was no historical trend for the birth prevalence of anencephaly comparing the two pre-fortified periods, but the relative risks were heterogeneous among hospitals in this comparison. There was a 42% (minimum 10%, maximum 63%) decrease in the birth prevalence rate of anencephaly in the fortified period as compared with the immediately pre-fortified period, with homogeneous relative risks among hospitals. Within the methodological constraints of this study we conclude that the birth prevalence rates for both spina bifida and anencephaly decreased as a result of folic acid fortification, without interference of decreasing secular trends.