Several studies have reported time of birth is associated with differences in obstetric practice. We investigated the relationship between timing of birth and obstetric and neonatal outcomes, to help plan working patterns under European Working Time Directive (EWTD) legislation. This was a retrospective observational study undertaken in a tertiary-level university teaching hospital. Data were derived froni the labour ward register of births for all women who delivered after 24weeks gestation in 2004. Births during on-call hours refer to those that occurred at weekends and after 1630 and before 0830 on weekdays.