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Antibiotics cut infection risk in obese women after caesarean

Surgical infection less likely if obese women take prophylactic antibiotics for 48h after C-section

Louise Prime

Wednesday, 20 September 2017

Obese women who took additional prophylactic antibiotics for 48 hours following a caesarean section delivery had less than half the risk of surgical site infection (SSI) compared with women who had only the standard intravenous preoperative cephalosporin, research has shown. The researchers behind the placebo-controlled study,* newly published in JAMA, suggested that prophylactic oral cephalexin and metronidazole might be warranted to reduce the risk of obese women developing SSI after caesarean delivery.

The team of US researchers, led from the university of Cincinnati, pointed out that the risk of SSI after caesarean delivery is known to be higher among obese women, and the rate of obesity in women has increased in the US – but the optimal antibiotic regimen to prevent SSI in these high-risk women had remained unknown.

They randomised more than 400 women having a caesarean section, whose pre-pregnancy body mass index (BMI) was at least 30, to one of two groups. All the women received standard preoperative intravenous cephalosporin, but the intervention group of 202 women also took 500mg oral cephalexin plus 500mg metronidazole every 8 hours for 48 hours following caesarean delivery, while the control group of 201 women took apparently identical placebo tablets every eight hours for 48 hours.

The researchers reported an overall rate of SSI (defined as any superficial incisional, deep incisional, or organ/space infections within 30 days after caesarean delivery) of 10.9%, but this varied markedly between the groups. The SSI rate was 6.4% in the cephalexin-metronidazole group, compared with 15.4% in the placebo group – a 59% reduction in relative risk. No serious events or allergic reactions were reported in either group.

The study authors acknowledged that it had certain limitations, for example that it was done at just one site at which the prevalence of obesity was high – so their findings might not be applicable to all obstetric units.

But they concluded: “For prevention of SSI among obese women after caesarean delivery, prophylactic oral cephalexin and metronidazole may be warranted.”


* Valent AM, DeArmond C, Houston JM, et al. Effect of post-cesarean delivery oral cephalexin and metronidazole on surgical site infection among obese women: a randomized clinical trial. JAMA 2017; 318(11): 1026–1034. doi:10.1001/jama.2017.10567.

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