Neonatal mortality in NHS maternity units by timing and mode of birth: a retrospective linked cohort study

To compare neonatal mortality in English hospitals by time of day and day of the week according to care pathway.

Retrospective cohort linking birth registration, birth notification and hospital episode data.

National Health Service (NHS) hospitals in England.

6 054 536 liveborn singleton births from 2005 to 2014 in NHS maternity units in England.

Neonatal mortality.

After adjustment for confounders, there was no significant difference in the odds of neonatal mortality attributed to asphyxia, anoxia or trauma outside of working hours compared with working hours for spontaneous births or instrumental births. Stratification of emergency caesareans by onset of labour showed no difference in mortality by birth timing for emergency caesareans with spontaneous or induced onset of labour. Higher odds of neonatal mortality attributed to asphyxia, anoxia or trauma out of hours for emergency caesareans without labour translated to a small absolute difference in mortality risk.

The apparent 'weekend effect' may result from deaths among the relatively small numbers of babies who were coded as born by emergency caesarean section without labour outside normal working hours. Further research should investigate the potential contribution of care-seeking and community-based factors as well as the adequacy of staffing for managing these relatively unusual emergencies.