Polk 1982.

Methods	RCT; 2 parallel groups. Unit of randomization: individual.
Participants	Dates of data collection: July 1978 to October 1980. Setting: Brigham and Women's Hospital, Boston, Massachusetts, US. Inclusion criteria: all women undergoing CS (other than repeat section); criteria do not correspond with our definition of non‐elective. N = 278. Exclusion: active infection, fever, membranes ruptured > 36 hrs, antibiotic therapy within 2 weeks, renal disease, allergy to penicillin or cephalosporin.
Interventions	Intervention: 1st generation cephalosporin: cefazolin 2 g after cord clamped and at 4 and 8 hrs after 1st dose; N = 146. Comparison: placebo: matching placebo; N = 132.
Outcomes	Fever (oral temperature > 100.3oF on any of 2 of 1st 10 post‐operative days); UTI, wound infection (only pus‐draining included in outcome of wound infection); endometritis (fever, tenderness on pelvic examination, abnormal discharge); pelvic abscess; septic pelvic thrombophlebitis, bacteremia; subsequent antibiotic use (23% for placebo vs 12% for treatment).
Notes	Outcome of fever and minor wound infection combined (11/146 for treatment vs 13/132 for placebo). 4 episodes of bacteremia, all in placebo group. 1 episode of rash and 1 episode of phlebitis reported in treatment group vs none in control. Data collected at 6 weeks on 259/266 patients; 35% of infections diagnosed after discharge. Class of antibiotic: 1st generation cephalosporin. Subgroups: type CS undefined; after cord clamping. The 2 groups were comparable regarding age, BMI, proportion on private service, etc.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomly allocated". Comment: no description of sequence generation process.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: 12 participants withdrawn (8 treatment, 4 placebo) and started on therapeutic antibiotics by the surgeon because the operation had been prolonged or was complicated or the pre‐operative specimen of urine disclosed significant bacteriuria; results on participants excluded could not be re‐included in ITT analysis.
Selective reporting (reporting bias)	Unclear risk	Comment: insufficient information to judge.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "Participants, their physicians and all investigators were unaware of the assignment throughout the study". Comment: double‐blind, matching placebo.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: probably outcome assessment was blinded.
Other bias	Low risk	Comment: no other sources of bias identified.