[Birth spacing: collaborative study of eight state maternities]

We collected data con 2,434 deliveries of live newborns (1.5% of the total for the country) in 8 state supported maternity wards of urban areas in Chile. First children, stillbirths and twins were excluded. Proportion of the sample according to city was: West Santiago 41%, Talcahuano 16%, Valparaíso 14%, Arica 8%, Chillan 7%, Valdivia 6%, Punta Arenas 6%, and Coyhaique 2%. The intergenesic interval was over 5 years in 38%, over 4 years in 48% and under 1 year in only 1.9% of cases, with minimal inter-city variation. Contraceptive agents were used by 26% of mothers with intergenesic interval under 1 year and 21% of those over 5 years, significantly higher than that found in the other intervals. Maternal age was between 20 and 29 years in 60%; only 8% of mothers were younger than 20 or older than 40 years of age. The incidence of cesarean section increased from 21 to 28.6% with increasing intergenesic interval. Mean weight of newborns was 3,338 g, significantly lower in the intergenesic interval under 1 year (3,251 g). The incidence of low birth weight was also highest in the latter group.