Introduction
Globally, the proportion of births which occur by caesarean delivery is increasing1 but the underlying drivers are poorly understood. Several attempts have been made to assess how temporal changes in individual maternal characteristics, obstetric practice, and maternal request for caesarean delivery have influenced this trend.2–5 Large observational studies in the United States have found that changes in maternal risk profile over time do not explain all the observed increases in caesarean rates, but these studies did not account for some factors such as age or body mass index (BMI).5,6 Others have reported that maternal BMI alone explains 9% to 14% of caesarean deliveries.2,7,8
In an Australian setting, the most common indications associated with recent increases in caesarean deliveries were previous caesarean delivery, slow progress in labour, and breech presentation.9 Additionally, the importance of primary caesarean delivery has been emphasized because it leads to planned repeat caesarean deliveries.10 However, we do not know how much of the overall rising caesarean delivery rate is being driven by overall temporal changes in maternal characteristics.
By understanding the underlying drivers of increases in rates of caesarean section, clinicians and health systems can better explore safe preventative measures. This is important because primary caesarean deliveries can increase morbidity and mortality, increase risks in future pregnancies, and many women would choose to avoid caesarean delivery if safe to do so.11,12
The aims of this study were to assess the contribution of demographic and clinical factors to changes in the caesarean delivery rate during the time when it increased from less than 20% to more than 30% of all births.