LAUSR

OBJECTIVE to analyze trends in cesarean sections proportion and associated factors in Piauí State, Brazil, from 2000 to 2011. METHODS this is a time series and cross-sectional study, with data of all institutional childbirths in primiparous, recorded on the Information System on Live Births (Sinasc). RESULTS cesarean sections proportion increased from 34.4% in 2000 to 52.1% in 2011 (annual percentage change +4.4; 95%CI 3.6;5.1); white-skinned women (PR=1.72; 95%CI 1.63;1.86), over 40 years (PR=2.17; 95%CI 2.09;2.28), with more than 12 years of schooling (PR=1.86; 95%CI 1.77;1.96), who attended 7 or more prenatal care appointments (PR=2.08; 95%CI 1.97;2.18), residents in municipalities with over 300,000 inhabitants (PR=1.68; 95%CI 1.62;1.80) and with higher Human Development Index (PR=1.61; 95%CI 1.51;1.73) presented the highest cesarean sections proportion. CONCLUSIONS the occurrence of cesarean sections was high and more frequent in women with low obstetric risk.