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Research from the Health Protection Agency (HPA) identified 394 surgical site infections among 4,107 women followed up after a caesarean section operation (9.6 per cent). The majority of these infections were minor (88 per cent) and the risk was found to be higher in overweight or obese women, according to findings published in the British Journal of Obstetrics & Gynaecology yesterday.

The study looked at data from 4,107 caesarean operations from 14 acute hospitals across England which were carried out in 2009.

This rate of infection is higher than would be expected for what is considered to be a relatively ‘clean’ operation i.e. not in an area of the body with high bacterial levels such as the large bowel. Using similar methods to identify infection risk, the rate of infection following a hysterectomy is 6.6 per cent and for operations in the large bowel it is 14.7 per cent.

Of the 394 women who developed an infection:

• 348 (88.3 per cent) were superficial incisional infections
  • These will clear up in a few days but will probably require antibiotic treatment.
• 19 (4.8 per cent) were deep incisional surgical infections affecting deeper tissues under the skin
  • These will require a course of antibiotics, along with possible hospitalisation and additional surgery on the wound in more serious cases. 
• 27 (6.9 per cent) were organ/space infections, 25 of which were classed as endometritis (infection of the lining of the womb) and two were other reproductive tract infections. 
  • These are infections which affect an internal body cavity. They can be debilitating to the patient; requiring a course of intravenous antibiotics, and hospitalisation in many cases.
• 23 (5.8 per cent) had to be readmitted to hospital for treatment of their infection (0.6 per cent of all the women)

There were a number of factors that were associated with the development of an infection; the strongest association was with BMI (Body Mass Index), with a weaker association to the age of the woman.

Obesity was strongly associated with development of a surgical site infection, with the risk of developing an infection, whether superficial, deep or organ/space, increasing the more overweight the woman was. Those who were overweight (BMI 25-30) were 1.6 times more likely to develop an infection, obese women (BMI 30-35) were 2.4 times more likely and those with a BMI over 35, 3.7 times more likely.

The research also found that younger women (those under 20, compared to those 25-30) were 1.9 times more likely to develop an infection. Reasons for this are not clear and more research is needed in this area.

Dr Elizabeth Sheridan, Head of Healthcare Associated Infections at the HPA, said: “Reducing rates of surgical site infections following a caesarean should be made a priority. Given that one in four women deliver their baby by caesarean section, these infections represent a substantial burden. They will impact not only directly on the mother and her family but also are a significant cost in terms of antibiotic use, GP time and midwife care and every effort should be made to avoid them. Women choosing to have caesarean section for non-medical reasons should be aware of the risk of infection, particularly if they are overweight.

“As has been seen in both this study and several others, there is an established link between BMI and an increase in the risk of developing a surgical site infection. Monitoring infections in women having a caesarean section is important as a means to drive down infection rates. As levels of obesity are rising, optimising surgical techniques and identifying the most appropriate dosing of antibiotics could provide a means for reducing wound infections in obese women.”

Notes for editors:

1. Fourteen general acute hospitals in seven Strategic Health Authorities (SHAs) took part in the research, recording data over 1-2 three month periods during the year. These hospitals already participate in the HPA’s Surgical Site Infection Surveillance Scheme. They belonged to hospital trusts which carried out between 2100-11,284 deliveries a year for 2009-10, 550 to 2742 of which were caesarean sections. All the hospitals had a special care baby unit, eight had a high dependency baby unit and eight had a neonatal intensive care unit.
2. The average time to infection was ten days. As the average length of hospital stay was 3 days, the majority of infections were detected after discharge. 
3. Causative microorganisms were recorded for 40 per cent of the infections (157/394). The bacteria causing the infections were bacteria originating from skin and/or vaginal flora and the respiratory tract. Of these infections 24.2 per cent (38/157) were reported to be polymicrobial (i.e. more than one type of bacteria cultured from the wound). The most commonly reported pathogen was Staphylococcus aureus (40 per cent) of which 17 per cent were meticillin-resistant (MRSA). Other pathogens included anaerobic cocci (23.2 per cent), Enterobacteriaceae (13.3 per cent) and streptococci (7.4 per cent).
4. Surveillance for surgical site infection following caesarean section is mandatory in Scotland, Wales and Northern Ireland. ARHAI (The Advisory Committee on Antimicrobial Resistance and Healthcare Associated Infection) recommended in 2010 that caesarean section surveillance should also be mandatory in England. The HPA are currently seeking funding to establish a caesarean section surveillance programme for England.
5. The Health Protection Agency is an independent UK organisation that was set up by the government in 2003 to protect the public from threats to their health from infectious diseases and environmental hazards. In April 2013, subject to the usual approvals procedures for establishing new bodies, the Health Protection Agency will become part of a new organisation called Public Health England, an executive agency of the Department of Health. To find out more, visit our website: http://www.hpa.org.uk or follow us on Twitter @HPAuk, or ‘Like’ us on Facebook at www.facebook.com/HealthProtectionAgency. 
6. For more information please contact the national HPA press office at Colindale on 0208 327 7901 or email colindale-pressoffice@hpa.org.uk.  Out of hours the duty press officer can be contacted on 0208 200 4400.