Background: Brazil has the highest caesarean section (CS) rate in the world (36.4% in 1996).
Methods: Risk factors for increasing CS rate were studied in two population-based cohorts of singleton live births in families residing in the municipality of Ribeirao Preto, State of Saõ Paulo, Southeast Brazil. The first comprised births from June 1978 to May 1979 (6750 births-one-year survey) and the second births from May to August 1994 (2846 births-4-month survey). Multiple unconditional logistic regression modelling was used to control for confounding.
Results: The CS rate rose from 30.3% in 1978-1979 to 50.8% in 1994. In 1978-1979, socioeconomic, reproductive and demographic variables, and health service factors were associated with CS rate. In 1994, only reproductive, demographic and health service factors remained associated, e.g. hour of delivery (from 7 a.m. to 12 p.m.), attendance by the same physician for prenatal care and delivery, > or =4 prenatal visits, maternal age > or =30 years, 1-3 previous live births and birthweight 3500-3999 g.
Conclusion: Caesarean section in Brazil is widely performed for non-medical reasons in which physician convenience plays an important role. There is an urgent need for public health interventions to reduce the CS rate in Brazil, mainly directed towards cultural beliefs and physician behaviour.