Wyatt 1998.

Methods	STUDY DESIGN: cluster RCT, hospital level Risk of Bias: MEDIUM
Participants	PROVIDERS: a total of 25 hospitals, 13 control and 12 intervention, targeting 2 providers (lead obstetrician and senior midwife manager) in each hospital PARTICIPANTS: 1318 episodes of care in 1318 patients, 25 clusters (hospitals) CLINICAL PROBLEM: administration of prophylactic antibiotics to women undergoing Caesarean section. The intervention also targeted 3 other care processes. SETTING: 25 district general (non‐teaching) hospitals POWER CALCULATION: As only 25 obstetric units were available for randomisation, and accurate baseline figures for the rates and variability of the 4 marker clinical practices were not available, sample size calculation was not carried out.
Interventions	FORMAT: educational meeting with dissemination of guideline and slides COMPARISON: 13 control hospitals with no intervention DESIRED CHANGE: increase effective
Outcomes	PRESCRIBING: Exposure: % women that received antibiotic prophylaxis
Notes	FINANCIAL SUPPORT: Funding: regional research implementation initiatives of the North Thames and South Thames regional health authorities; the Imperial Cancer Research Fund; and North Staffordshire Hospital Trust. Competing Interests: none declared ADDITIONAL DATA: no response from authors to request for additional data
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Obstetric units were allocated to intervention or control group by the toss of a coin.
Allocation concealment (selection bias)	Low risk	To eliminate bias during data collection at follow‐up by a second research midwife, and to allow blinded assessment of guideline quality, the allocation was concealed from everyone except JCW, DGA, RJ, and the first research midwife.
Blinding (performance bias and detection bias) All outcomes	Low risk	To eliminate bias during data collection at follow‐up by a second research midwife, and to allow blinded assessment of guideline quality, the allocation was concealed from everyone except JCW, DGA, RJ, and the first research midwife.
Incomplete outcome data (attrition bias) All outcomes	Low risk	"No unit was excluded after randomisation, all intervention units participated in the visits, and data on clinical practices were available for all units, although smaller numbers of case notes were obtainable than planned for steroid usage"
Selective reporting (reporting bias)	Low risk	See above
Other bias	Low risk	"To reduce the impact of ceiling effects, the proportion of cases in which clinicians failed to carry out each clinical practice was recorded for each obstetric unit at baseline and follow up, and then baseline to follow up ratios were computed to yield the risk ratio for failure to implement each practice in each unit."
Baseline Outcomes similar?	Unclear risk	"Accurate baseline figures for the rates and variability of the four marker clinical practices were not available"
Free of contamination?	Low risk	Randomisation by units that were located in different hospitals
Baseline characteristics similar?	Low risk	"Despite randomisation there were baseline differences in two of the four clinical practices" (use of ventouse and use of polyglycolic acid sutures). "There were no other baseline differences." (includes antibiotic prophylaxis)