A systematic literature review of the influence of epidural analgesia during labour and the Caesarean section rate [1] provides an insight into how information collected from studies with different designs may be combined. It also answers the question: "how much extra risk is there of a woman having a Caesarean if she has an epidural?"

The review -- The authors (from California) did a thorough review of the literature, including use of Effective Care in Pregnancy and Childbirth and contacting experts to locate studies. They read 230 manuscripts before settling on six for inclusion. Four of these were retrospective design - three reviewing all women delivered during a specified period, and one with a matched case control design. The other two were randomised controlled trials (RCTs).

Data extraction -- The Caesarean delivery rate for epidural and non-epidural groups was extracted from the six reports.

Results -- Bandolier took the data from each study and plotted the Caesarean rate for epidural and non-epidural groups on a L'Abbé plot with the numbers of women included in each study, and calculated odds ratio and NNT. There was a consistent increase in Caesarean section rate in women having epidural analgesia. The overall weighted difference was 10%, generating an NNT of 10 (95%CI 8.4 - 13), with an odds ratio of 2.6 (2.1 - 3.2).

This means that for every 10 women in labour having epidural analgesia, one more will have a Caesarean section, who would not have done had they had another form of analgesia.

Comment -- The NNT of 10 provides a figure which can be used by women and their caregivers in making choices about their labour. It was interesting that in this case both randomised and non-randomised designs produced the same estimate of effect. The paper discusses the issue of more complicated deliveries, and private and state health care, without making any startling conclusions. It is a useful read.

Reference: 1.SC Morton, MS Williams, EB Keeler, JC Gambone, KL Kahn. Effect of epidural analgesia for labor on the Cesarean delivery rate. Obstetrics & Gynecology 1994 83: 1045-52.

http://www.jr2.ox.ac.uk/Bandolier/band34/b34-3.html

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