OBJECTIVE: to investigate factors associated with having a caesarean section, with special emphasis on women's preferences in early pregnancy. DESIGN: a cohort study using data from questionnaires in early pregnancy and 2 months after childbirth, and data from the Swedish Medical Birth Register. SETTING: women were recruited from 97% of all antenatal clinics in Sweden at their booking visit during 3 weeks between 1999 and 2000, and followed up 2 months after birth. PARTICIPANTS: a total of 2878 Swedish-speaking women were included in the study (87% of those who consented to participate and 63% of all women eligible for the study). FINDINGS: Of 236 women who wished to have their babies delivered by caesarean section when asked in early pregnancy, 30.5% subsequently had an elective caesarean section and 14.8% an emergency caesarean section. The logistic regression analyses showed that, a preference for caesarean section in early pregnancy (odds ratio [OR] 9.63, 95% confidence interval [CI] 5.94-15.59), a medical diagnosis (OR 9.03, 95% CI 5.68-14.34), age (OR 1.08, 95% CI 1.03-1.13), parity (OR 0.58, 95% CI 0.37-0.91), a previous elective caesarean section (OR 15.11, 95% CI 6.83-33.41) and a previous emergency caesarean section (OR 18.29, 95% CI 10.00-33.44) was associated with having an elective caesarean section. Having an emergency caesarean section was associated with a preference for a caesarean section (OR 2.59, 95% 1.61 to 4.18), a medical diagnosis (OR 4.12, 95% CI 2.91-5.88), age (OR 1.08, 95% CI 1.05-1.12), primiparity (OR 3.34, 95% CI 1.78-6.27), a previous emergency caesarean section (OR 10.69, 95% CI 6.03-18.94), and a previous elective caesarean section (OR 7.21, 95% CI 2.90-17.92). KEY CONCLUSIONS AND IMPLICATIONS FOR PRACTICE: a woman's own preference about caesarean section was associated with the subsequent mode of delivery. Asking women about their preference regarding mode of delivery in early pregnancy may increase the opportunity to provide adequate support and possibly also to reduce the caesarean section rate.