[Chromosome aberrations in malformed newborns].
OBJECTIVE
To determine the prevalence of chromosome abnormalities in malformed newborn infants and to analyze the distribution of the types of anomalies, and the variation in their frequency with maternal age.


METHODS
We used the data collected according to the Spanish Collaborative Study of Congenital Malformations (ECEMC) methodology from March 1982 -September 1996. Of 33,562 newborns (live and stillborn), 1,409(4.1%) malformed infants were identified. A total of 332 karyotypes were performed in peripheral blood, representing 23.5% of the newborns with congenital defects. Results The frequency at birth of chromosome abnormalities was 5.4% of malformed newborns. There were 59 infants with Down's syndrome, 6 with trisomy 18, 3 with Turner's syndrome, 2 with trisomy 13, 2 with "Triple X", 1 tetraploidy, 1 triploidy, 1 trisomy 9 p, and 1 infant with a complex XXY mosaicism. The prevalence of Down's syndrome in the general population is 0.17%. The mean age of mothers with Down's syndrome infants was 34.2 years and paternal age was 36 years, and a non-statistically significant diminishing trend in mean maternal age was observed during the course of the study. The prevalence of Down's syndrome was higher in mothers aged more than 35 years. A non-statistically significant increase of the prevalence of Down's syndrome in newborns with mothers aged between 31 and 34 years was observed with time. The mean number of previous pregnancies was 2.81. Among a total of 49 mothers and fathers, two chromosome alterations were found.


CONCLUSIONS
The prevalence of chromosome abnormalities in newborns with birth defects was 5.4%. The frequency of Down's syndrome was higher. Down's syndrome was more prevalent in mothers aged more than 35 years. The mean maternal age of Down's syndrome infants gradually diminished, and accumulated between the ages of 31 and 34 years.
Centeno Malfaz
F
F
Servicio de Pediatría. Hospital Universitario del Río Hortega. Valladolid. centeno@uva.es
Beltrán Pérez
A
A
Ruiz Labarga
C
C
Centeno Robles
T
T
Macías Pardal
J
J
Martín Bermejo
M
M
D002869:Chromosome Aberrations; D000013:Congenital Abnormalities / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D010290:Parents; D015995:Prevalence