“High caesarean rates are not down to women being 'too posh to push'” says The Daily Telegraph. The newspaper said that a UK study has found that though there is a large variation in caesarean rates in England, most of the decisions to carry out the operation are made in emergency situations rather than mothers asking for surgery when they do not need it.
The large review underlying this report was an analysis of 620,604 single baby births at 146 hospital trusts in England in 2008. The report found a large unexplained variation in the rates of caesarean birth from 14.9% to 32.1%, (average 24%). However, this was mostly due to differences in the number of emergency rather than planned caesareans. As the newspapers point out, this appears to show that the ‘cliché’ that many women are asking for a caesarean rather than going through natural childbirth to be a ‘myth’.
This well-conducted study makes the case for further examination of the reasons behind the variation seen in emergency caesarean section rates between regions. Careful audit of the reasons and thresholds for emergency caesareans may be a way that the consistency of care for pregnant women could be improved.
Where did the story come from?
The study was carried out by researchers from the London School of Hygiene and Tropical Medicine, and other institutions in London. It was partly funded by an award from the Department of Health and the NHS research and development programme. The study was published in the peer-reviewed British Medical Journal.
Most news sources focused on the finding that the high proportion of caesareans is unlikely to be due to high numbers of women with low-risk pregnancies asking for caesareans. Some speculate on the reasons for the variation in caesarean rates. For example, the BBC quotes one expert as saying, “The massive driving force in the rise of caesarean sections is the threat of litigation faced by hospitals and clinical teams”.
What kind of research was this?
This was a cross-sectional study using routinely collected hospital episode statistics.
The authors explain that the proportion of women having a caesarean section varies considerably between English NHS trusts. Rates are higher in the south of England compared with the north. Potential explanations for this include differences in the clinical needs of the local population; an increase in the number of women without risk factors asking for caesarean sections: a lack of midwives, and different attitudes and practices among professionals. However, few studies have adequately adjusted for these possible reasons. In this study, the researchers analysed the rates of caesarean section in singleton births, across NHS trusts and regions, over the course of a year to see whether the variation could be explained by a group of seven potential factors.
One main limitation of this study is that the data was collected routinely, which raises the possibility that the data collection is not complete. In addition, there may be other risk factors for caesarean sections that were not collected and which could have explained some of the variation between rates.
What did the research involve?
The researchers used data from the hospital episode statistics database, which contains records of all NHS patient admissions. Women admitted in pregnancy have data entered on their age and basic demographics, region of residence, and hospital administrative and clinical details.
Diagnostic information is recorded using codes from the International Classification of Diseases (ICD-10). Operative procedures are coded using the UK Office for Population Censuses and Surveys classification (OPCS). For example, an elective caesarean section was defined by OPCS code R17.
Following the birth of a baby, the system also captures information on the births, including onset of labour, number of pregnancies, birth weight, and length of pregnancy. The researchers say that only about 75% of delivery records in the database have this information.
The researchers looked for data held on all women aged between 15 and 44 with a singleton (not twin or multiple) birth between January 1 and December 31 2008. They used the rate of caesarean sections per 100 births (live or stillborn) as the main outcome for their analysis. They also adjusted for the following risk factors, identified in the ICD- 10 coding, and basic demographic information:
- parity (number of previous births)
- socioeconomic deprivation
- previous caesarean section
- breech presentation
- foetal distress
What were the basic results?
Among 620,604 single-baby births, 147,726 (23.8%) were delivered by caesarean section.
The adjusted rates of caesarean section ranged from 14.9% to 32.1% between different NHS trusts.
Women were significantly more likely to have a caesarean section if they had had one previously (70.8%) or had a baby with breech presentation (89.8%). About 72% of elective caesareans were performed for breech presentation or a previous caesarean section and this rate was similar for all NHS Trusts.
There was greater variation between trusts in the rates of emergency caesarean section than there was for rates of elective caesarean section. The unadjusted rates also appeared to demonstrate a ‘north-south’ divide, with more caesarean sections being carried out in the southerly NHS trusts. However, after the seven risk factors were taken into account, the apparent north-south divide disappeared.
How did the researchers interpret the results?
The researchers say that because the characteristics of the women giving birth in different NHS trusts can vary, comparing unadjusted rates of caesarean section should be avoided.
This is borne out by their finding that some issues “apparent in unadjusted rates of caesarean section, such as the north-south divide, disappear once maternal characteristics and clinical risk factors are taken into account”.
They also suggest that it is unlikely that the variations are affected much by high numbers of low-risk women asking for caesarean sections. This is because most women having a caesarean section in 2008 had at least one clinical risk factor, and there is little variation in adjusted rates of elective caesarean section between areas.
They say that, instead, the most variation was observed in the use of emergency caesarean section.
This carefully conducted analysis of the data held in the NHS database of patient admissions has produced a picture that goes some way to explaining the variations in caesarean rates between hospital trusts and regions of England. The finding that high rates are due to doctors' decisions rather than the personal choice of mothers is important, and removes the persistent 'too posh to push' myth.
The study has suggested alternative reasons for these variations, but cannot confirm these. Differences in the main indications for emergency caesarean section are thought to underlie the variation. For instance, doctors may have different thresholds for suggesting a caesarean when labour becomes complicated by things such as foetal (baby) distress or slow progression.
Some points to note about this study:
- The researchers captured almost all the data held on births in England for one year. This is a clear strength of the analysis,
- The downside of this is that inaccuracies could have occurred in the coding for the method of delivery, or the reasons behind it, and the researchers were not able to check the accuracy of the data from such a large population.
- Factors that could have been used to adjust the rates further (such as duration of pregnancy and birth weight) were not sufficiently recorded to allow them to be included in the analysis.
Overall, this study makes the case for further examining the reasons for the regional variation in rates of emergency caesarean section. An accompanying editorial points out that ‘unwarranted variation in clinical practice has been cited as an indication of a poor quality service’. Carefully auditing the reasons and thresholds for emergency caesareans may be a way of improving the consistency of care for pregnant women.