Factors associated with preterm births in Southeast Brazil: a comparison of two birth cohorts born 15 years apart

An increase in preterm deliveries in Ribeirao Preto stimulated an analysis of possible explanatory factors. Two cohorts of singleton livebirths were s tudied, the first based on 6746 births in 1978-9 and the second based on 28 46 births in 1994. A logistic regression was carried out to assess the asso ciation of preterm birth with several socio-demographic, behavioural and cl inical variables, including year of survey. Delivery in private settings co mpared with a public setting, maternal age of less than or equal to 17 comp ared with any other age group, and mothers who had had previous abortions a nd previous stillbirths were associated with greater rates of preterm birth . Although there was an increase in preterm birth rates regardless of mode of delivery, the increase was greater in the caesarean section group than i n the vaginal delivery group. Over the study period, deliveries in private hospitals and caesarean section operations increased markedly (from 4% to 3 6% and from 30% to 51% respectively). Caesarean section may be the main con tributor to the increase of preterm birth rate in this study. It is essenti al to ensure that health-care staff, especially those in private facilities , are properly educated and audited.