Objective: to establish which factors are associated with birthing positions throughout the second stage of labour and at the time of birth. Design: retrospective cohort study. Setting: primary care midwifery practices in the Netherlands. Participants: 665 low-risk women who received midwife-led care. Measurements and findings: a postal questionnaire was sent to women 3-4 years after birth. The number of women who remained in the supine position throughout the second stage varied between midwifery practices, ranging from 31.3% to 95.9% (p<0.001). The majority of women pushed and gave birth in the supine position. For positions used throughout the second stage of labour, a stepwise forward logistic regression analysis was used to examine effects controlled for other factors. Women aged ≥36 years and highly educated women were less likely to use the supine pushing position alone [odds ratio (OR) 0.54, 95% confidence intervals (CI) 0.31-0.94; OR 0.40, 95% CI 0.21-0.73, respectively]. Women who pushed for longer than 60 minutes and who were referred during the second stage of labour were also less likely to use the supine position alone (OR 0.32, 95% CI 0.16-0.64; OR 0.44, 95% CI 0.23-0.86, respectively). Bivariate analyses were conducted for effects on position at the time of birth. Age ≥36 years, higher education and homebirth were associated with giving birth in a non-supine position. Key conclusions: the finding that highly educated and older women were more likely to use non-supine birthing positions suggests inequalities in position choice. Although the Dutch maternity care system empowers women to choose their own place of birth, many may not be encouraged to make choices in birthing positions. Implications for practice: education of women, midwives, obstetricians and perhaps the public in general is necessary to make alternatives to the supine position a logical option for all women. Future studies need to establish midwife, clinical and other factors that have an effect on women's choice of birthing positions, and identify strategies that empower women to make their own choices. © 2007 Elsevier Ltd. All rights reserved.