Variation in and factors associated with timing of low risk, pre-labour repeat caesarean sections in NSW, 2008-2011

To explore variation in public hospital rates of early (37-38 weeks gestation) prelabour repeat caesarean section among low-risk women at and beyond term in New South Wales (NSW) between 2008 and 2011. IMPORTANCE OF THE STUDY: A NSW Ministry of Health policy directive for public hospitals (PD2007_024), 'Maternity - timing of elective or pre-labour caesarean section', requires that low-risk elective or prelabour caesarean section does not occur before 39 completed weeks gestation. However, compliance with this policy has not been evaluated.

Population-based record linkage study Methods: Linked birth and hospital data for low-risk, prelabour repeat caesarean sections in NSW in 2008-2011 were analysed using multilevel regression modelling. Rates were adjusted for casemix and hospital factors. Low-risk pregnancies were defined as singleton live births at 37-42 weeks gestation among women without medical or obstetric complications and where the indication for caesarean section was 'elective repeat caesarean section'.

In 2008-2011, there were 15 163 prelabour repeat caesarean sections among low-risk women in NSW. Overall, 34.7% of low-risk prelabour repeat caesarean sections occurred before 39 weeks gestation. Adjusted NSW public hospital rates of early (37-38 weeks gestation) low-risk prelabour repeat caesarean section varied widely (16.3-67.5%). Adjusting for casemix factors actually increased the between-hospital variation by 4.3%; adjusting for hospital factors reduced variation by 20.0%. Smoking, private healthcare, assisted reproductive technology use, higher parity, a noncaesarean uterine scar and delivering in a hospital with CPAP (continuous positive airway pressure) facilities were associated with higher odds of early delivery, although infants that were small for gestational age were associated with lower odds. Hospitals with higher rates of low-risk deliveries and higher propensity for vaginal birth after caesarean section had lower odds of early delivery.

The findings suggest generally poor compliance with the policy directive that prelabour caesarean does not occur before 39 weeks gestation, with adjusted compliance rates ranging from 32.5% to 83.7%. Large between-hospital variation after adjustment suggests that nonmedical factors are related to timing of low-risk prelabour repeat caesarean sections. Further strategies are needed to improve adherence to this evidence based policy.