Abstract: We included 10 studies (1354 women). The risk of bias was unclear or high in most of the included studies. All of the included trials involved women undergoing caesarean section whether elective or non-elective. Intravenous antibiotics versus antibiotic irrigation (nine studies, 1274 women) Nine studies (1274 women) compared the administration of intravenous antibiotics with antibiotic irrigation. There were no clear differences between groups in terms of this review's maternal primary outcomes: endometritis (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.70 to 1.29; eight studies (966 women) (low-quality evidence)); wound infection (RR 0.49, 95% CI 0.17 to 1.43; seven studies (859 women) (very low-quality evidence)). The outcome of infant sepsis was not reported in the included studies. In terms of this review's maternal secondary outcomes, there were no clear differences between intravenous antibiotic or irrigation antibiotic groups in terms of postpartum febrile morbidity (RR 0.87, 95% CI 0.48 to 1.60; three studies (264 women) (very low-quality evidence)); or urinary tract infection (RR 0.74, 95% CI 0.25 to 2.15; five studies (660 women) (very low-quality evidence)). In terms of adverse effects of the treatment on the women, no drug allergic reactions were reported in three studies (284 women) (very low-quality evidence), and there were no cases of serious infectious complications reported (very low-quality evidence). There was no clear difference between groups in terms of maternal length of hospital stay (mean difference (MD) 0.28 days, 95% CI -0.22 to 0.79 days, (random-effects analysis), four studies (512 women). No data were reported for the number of women readmitted to hospital. For the baby, there were no data reported in relation to oral thrush, infant length of hospital stay or immediate adverse effects of the antibiotics on the infant. Intravenous antibiotic prophylaxis versus oral antibiotic prophylaxis (one study, 80 women) One study (80 women) compared an intravenous versus an oral route of administration of prophylactic antibiotics, but did not report any of this review's primary or secondary outcomes. There was no clear difference between irrigation and intravenous antibiotic prophylaxis in reducing the risk of post-caesarean endometritis. For other outcomes, there is insufficient evidence regarding which route of administration of prophylactic antibiotics is most effective at preventing post-caesarean infections. The quality of evidence was very low to low, mainly due to limitations in study design and imprecision. Furthermore, most of the included studies were underpowered (small sample sizes with few events). Therefore, we advise caution in the interpretation and generalisability of the results. For future research, there is a need for well-designed, properly-conducted, and clearly-reported RCTs. Such studies should evaluate the more recently available antibiotics, elaborating on the various available routes of administration, and exploring potential neonatal side effects of such interventions.

Plain-language summary: We searched for evidence from randomised controlled trials on 6 January 2016 and found 10 studies (involving a total of 1354 women). Nine studies (1274 women) compared intravenous antibiotic administration with antibiotic irrigation (washing with a saline solution containing antibiotics). The two routes gave similar results on important outcomes including infection of the uterus/womb (low-quality evidence) and wound infection (very low-quality evidence). The studies did not report on blood infections in the newborn infant (sepsis). The numbers of women who had urinary tract infection (very low-quality evidence), serious infectious complications (very low-quality evidence) or fever after birth (very low-quality evidence) also did not clearly differ between groups. There was no clear difference between groups in terms of how long women spent in hospital and no data reported on the number of women who were readmitted to hospital. No women had allergic reactions to the antibiotics (very low-quality evidence) in the three studies that reported this outcome. None of the studies reported information about whether the babies had any immediate adverse reactions to the antibiotics. One study (involving 80 women) compared intravenous antibiotics with taking antibiotics orally but it did not report on any of this review's outcomes. The studies included in this review did not clearly report how they were carried out and outcome data were incomplete. Too few women were included in each study for sufficient numbers of events to see a clear difference in outcomes between the two groups of women. This meant the evidence was of low quality. Therefore, we need to exercise caution in the interpretation and generalisability of the results. High-quality studies are needed to determine the safest, most effective way of giving preventive antibiotics. Such studies should evaluate more recently available antibiotics and consider potential side effects that the intervention may have for the baby.