Obstetrical interventions for term first deliveries in the US

Labour induction and caesarean are increasingly done without clinical indication. However, little is known about the prevalence of such interventions, or the characteristics of women who receive them. We used the 2003 revision of the US birth certificates to summarise recorded interventions and to characterise maternal profiles associated with such interventions.

We carried out a retrospective study of 2.35 million primiparous women delivering singleton live births at 37-44 weeks in the US from 2005 to 2008. We used the 2003 revision of the birth certificate to define delivery categories: 'indicated' were those with induced labour or pre-labour caesarean for hypertension, diabetes, chorioamnionitis, failed cephalic version at ≥40 weeks, growth restriction (<3rd centile), or post-term (≥42 weeks); those with pre-labour caesarean with breech at ≥39 weeks; or those with caesarean with labour lasting ≥12 h, failed trial of labour, vacuum/forceps extraction, or fetal intolerance to labour. Remaining deliveries with induction/caesarean were classified as 'non-indicated' and all other deliveries 'spontaneous'.

Half of all term first births (50%) were delivered after intervention, and half of interventions were non-indicated (26% of all deliveries). Women with interventions were more likely to deliver on a weekday. Non-indicated interventions were more common among socially advantaged women.

Nearly a quarter of US term first deliveries had an indicated intervention, and another quarter received intervention without a recorded clinical indication. Both numbers are probably underestimates.