Several resource-rich countries have responded to the public health concern posed by high caesarean section rates by implementing policies designed to increase the rate of normal vaginal birth. In the UK,⁵ the USA⁶ and New South Wales (NSW)⁷ government policy has been implemented with the explicit aim of increasing the vaginal birth rate and decreasing the caesarean section rate.⁷ Despite these efforts, intervention in childbirth continues to increase in Australia and many other developed nations.

The cost to the tax payer of the rising intervention in childbirth is significant.^{8 9} A recent Australian randomised controlled trial of caseload midwifery care for women in all risk categories showed that care in less interventionist models was as safe and significantly less costly than routine public hospital care (in press). In 2000 Roberts, Tracy and Peat published a paper examining rates of obstetric intervention among private and public women giving birth in NSW during the years 1996 and 1997. NSW is the most populous state in Australia and broadly representative of the national population. The Roberts et al¹⁰ study found that the number of women classified as low risk was similar (48%) among those receiving private obstetric care and those receiving standard public hospital care. Rates of obstetric intervention among these low-risk women were however significantly higher among women giving birth under private obstetric care. Among the low-risk primiparous women giving birth during this period, more women giving birth in private hospitals compared to public hospitals had forceps and vacuum deliveries (34% vs 17%), induction of labour (26% vs 16%), caesarean section (16% vs 10%), epidural (51% vs 25%) and episiotomy (47% vs 29%).¹⁰ The small number of private women who gave birth in public hospitals had lower intervention rates than in private hospitals and higher intervention rates than women who were not privately insured.

Overall women who gave birth in private hospitals were more likely to be over 35 years of age and have a baby at or above the 90th centile for birth weight and gestation. They were less likely to have four or more children, have a pregnancy-related medical condition, have a baby weighing less than the 10th centile, weighing under 2500 g, born at less than 37 weeks gestation, have a pregnancy before the age of 20 or have a pregnancy lasting beyond 41 weeks (table 1).

Table 2 shows the rate of obstetric intervention among the 30 152 low-risk primiparous women who gave birth in a private hospital and the 94 279 low-risk primiparous women who gave birth in a public hospital. Low-risk primiparous women giving birth in a private hospital compared to a public hospital had higher rates of induction (31% vs 23%), instrumental birth (29% vs 18%), caesarean section (27% vs 18%), epidural (53% vs 32%) and episiotomy (28% vs 12%) and they had a 20% lower normal vaginal birth rate (44% vs 64%). Intervention rates for low-risk primiparous women had increased substantially between 1996/1997 and 2000/2008, except for episiotomy and forceps delivery where there had been a decline.

Table 3 shows the rate of intervention among 30 512 low-risk multiparous women who gave birth in a private hospital compared to 138 897 low-risk women who gave birth in a public hospital. Low-risk multiparous women had higher rates of instrumental birth (7% vs 3%), caesarean section (27% vs 16%), epidural (35% vs 12%) and episiotomy (8% vs 2%) and 15% lower normal vaginal birth rates (66% vs 81%) when giving birth in a private hospital. Intervention rates for low-risk multiparous women had increased substantially between 1996/1997 and 2000/2008, except for episiotomy and forceps delivery where there had been a decline. There appears to have been an increase in severe perineal trauma among low-risk multiparous women in private as well as public hospitals since 1996/1997.

Over the past decade, the rate of birth interventions such as caesarean section for low-risk women had nearly doubled in private hospitals (figures 1 and ​and2).2). Obstetric interventions steadily increased among low-risk women receiving public hospital care during this period by more than 5%, and by over 10% among women receiving private obstetric care in private hospitals. Table 4 shows the cascade effect of obstetric interventions among low-risk primiparous women when standardised for age. There was a notable increase in intervention and decline in normal vaginal birth as the interventions accumulated (induction of labour, epidural and augmentation of labour). Low-risk primiparous women giving birth in a private hospital were more likely to have interventions during labour and more likely to have operative births. Among low-risk primiparous women giving birth in private hospitals 15 per 100 women had a vaginal birth with no obstetric intervention compared to 35 per 100 women giving birth in a public hospital. This showed a reduction in rates of vaginal birth with no obstetric intervention compared to the previous study (18 per 100 women in private hospitals and 39 per 100 women in public hospitals)¹⁰ (figures 1 and ​and2).2). Among primiparous women giving birth in private hospitals that had an epidural the most likely outcome was an instrumental birth and this rate was higher than for women giving birth in a public hospital (40% vs 30%). The likelihood of having a vaginal birth also dropped significantly for these women (36% vs 47%). This difference was less dramatic with multiparous women but the high rates of pre-labour caesarean section among the women giving birth in a private hospital impacted on these outcomes. Among low-risk multiparous women, 35 per 100 women had a vaginal birth with no obstetric intervention compared to 65 per 100 women giving birth in a public hospital (table 5).

Our study is limited to providing a snapshot view of the birth outcomes in a defined time period. However, this study repeats the analysis of a paper published in 2000 providing the reader with a more detailed picture of the current state of obstetric intervention in NSW. The advantages of using population-based datasets, such as the MDC, include the size of the dataset and the guaranteed accuracy of a validated dataset. The limitations are the restricted number of variables that are included and the scarcity of specific information on potential confounders. Previous validation studies have reported high levels of data accuracy for the majority of diagnoses and procedures conducted during labour and delivery in the state-wide data base,^{19 20} although the recording of medical conditions are overall generally underreported.^{19 21} While we could not control for obesity due to lack of reliable data, women who have private health insurance have lower rates of obesity and higher socioeconomic status hence these health disadvantages are most likely over-represented in the public women.²² There are also several other sociodemographic factors we could not control for such as education and income that increase risk for the women giving birth in public hospitals.

The overall proportions of women classified as low risk who gave birth in private and public hospitals in NSW during the years 2000–2008 were similar for primiparous women but significantly different for multiparous women. A decade ago 48% of women in private and public hospitals were considered low risk. This compares with 43% in our study a decade later. In NSW, the caesarean section rate has increased from 19% in 1998 to 30.2% in 2009.¹⁶ The caesarean section rate is much higher for the private sector and has been accompanied by an even sharper rise over the past decade as seen in our research. MacDorman et al²³ suggested that the rapid increase in the caesarean section rate from 1996 onward in the USA reflected two current trends: an increase in the primary caesarean section rate and a steep decline in vaginal birth after a primary caesarean section. A similar pattern is seen in Australia with increasing primary caesarean and repeat caesarean section rates.¹ It is commonly asserted that the rise in the caesarean section rate is due to changing demographics, such as older women, obese women and more complex medical profiles, which are a reality today in many resource rich nations. However, in our study, which only included low-risk women, the rise in caesarean section was independent of these factors. Other studies and government reports have also shown the dramatic rise in caesarean section independent of these risk factors.^{1 23 24}

Most concerning in this study was the fact that a low-risk primiparous woman has a 20% lower chance of having a normal birth (44%) if she gives birth in a private hospital under obstetric care in NSW than in a public hospital (64%). The implications for women and babies in terms of short-term and long-term morbidity^{3 4 25} are not insignificant. The cost of high intervention rates in childbirth is also significant to society. Tracy and Tracy⁸ studied the incremental cost increase to the public purse as interventions were introduced in the labour and birth process. They found that the relative cost of birth increased by up to 50% for low-risk primiparous women and up to 36% for low-risk multiparous women as labour interventions accumulated. An epidural was associated with a sharp increase in cost of up to 32% for some primiparous low-risk women, and up to 36% for some multiparous low-risk women. Private obstetric care increased the overall relative cost by 9% for primiparous low-risk women and 4% for multiparous low-risk women.⁸