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Smaill F, Hofmeyr GJ. Antibiotic prophylaxis for Cesarean section. Cochrane Review, latest version 25 Feb 1999. In: The Cochrane Library. Oxford: Update Software.
In women having caesarean delivery (c-section), does antibiotic prophylaxis reduce the incidence of endometritis, fever, wound infection, urinary tract infection (UTI), or other serious infection?
Studies were identified by using the specialised register of controlled trials for the Cochrane Pregnancy and Childbirth review group.
Studies were selected if they were randomised controlled trials that compared any prophylactic antibiotic regimen with placebo or no treatment for c-section.
Data were extracted on setting, antibiotic regimen, and methodological quality. Main outcomes were endometritis; fever; wound infection; UTI; and other serious infection (bacteraemia, septic shock, septic thrombophlebitis, nec-rotising fasciitis, or death from in-fection).
66 trials (9365 patients) were included. No significant heterogeneity existed among the trials. When all trials of c-section were combined, antibiotic prophylaxis reduced the rates of all out-comes (Table). Similarly, event rates were also reduced in trials of non-elective c-section and in trials that included both elective and non-elective c-sections. In trials of elective c-section, endometritis (6 trials) and fever (5 trials) were less frequent, but the rates of wound infection (7 trials), UTI (4 trials), and serious infection (2 trials) were not affected by antibiotics.
In women having caesarean delivery, antibiotic prophylaxis reduces the incidence of endometritis, fever, wound infection, urinary tract infection, and other serious infection.
Source of funding: UNDP/UNFPA/WHO/World Bank.
For correspondence: Dr. F. Smaill, Department of Laboratory Medicine, Chedoke-McMaster Campuses, Hamilton Health Sciences Corporation, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada. FAX 905-521-5099.
Antibiotic prophylaxis vs no prophylaxis for caesarean delivery*
Outcomes Number Weighted event rates RRR (95% CI) NNT (CI)
of trials Prophylaxis No prophylaxis
Endometritis 66 7.7% 20.7% 63% (58 to 67) 8 (7 to 9)
Fever 37 16% 34% 54% (50 to 59) 6 (5 to 7)
Wound infection 61 3.7% 9.4% 60% (53 to 66) 18 (15 to 22)
Urinary tract 49 5.2% 9.4% 45% (34 to 53) 24 (19 to 34)
Serious infection 29 1.0% 2.6% 56% (32 to 71) 63 (40 to 143)
*Abbreviations defined in Glossary; NNT and CI calculated from data in article.
Randomised trials in the late 1970s suggested that women would benefit from anti-biotic prophylaxis at the time of c-section. Since then, many more trials have been done, including this Cochrane review by Smaill and Hofmeyr, all of which support this intervention. But antibiotic prophylaxis is not uniformly practiced in my hospital, and I suspect many other hospitals are similar in this regard. Why isn't this being done? One argument is that the studies are too old, with only 8 of the 66 trials in this review published in the 1990s (although the year of publication had no apparent effect on the size of the treatment effect). Another reason is that advances in surgery have led to lower infection rates than those reported in the trials. Such arguments sound like an attack of David Sackett's killer Bs (1). This meta-analysis clearly shows a reduction in postoperative infection with antibiotic prophylaxis. Using endometritis as an example, the relative risk reduction when using antibiotic prophylaxis is 61% for non-elective c-sections and 75% in elective c-sections. The observed absolute risk reduction in this meta-analysis indicates that one only needs to treat 7 (95% CI 6 to 8) women having non-elective and 20 (CI 13 to 44) women having elective c-sections to prevent 1 patient from developing endometritis.
Although the arguments against antibiotic prophylaxis persist, it should be pointed out that even if the infection rate at one's hospital is only 50% of that of the control groups in this review (14% for non-elective and 3.3% for elective), the numbers needed to treat are still very favourable (i.e., 12 and 42, respectively). Given the results of this meta-analysis and that of another review in the same issue of the Cochrane Library (2) (showing that ampicillin or a first-generation cephalosporin is sufficient for prophylaxis in women having c-section and need only be given once to be effective), it is hard to justify not offering anti-biotic prophylaxis to all women requiring c-section.
Robert F. Burrows, MD?
Clayton, Victoria, Australia
1. Sackett D. Guidelines and killer Bs [EBM Note]. Evidence-Based Medicine. 1999 Jul-Aug;4:100-1.
2. Hopkins L, Smaill F. Antibiotic prophylaxis regimens and drugs for caesarean section. Cochrane Review, latest version 1 Nov 1998. In: The Cochrane Library. Oxford: Update Software.