Phelan 1979.

Methods	Randomized, placebo‐controlled trial; 2 parallel groups. Unit of randomization: individual.
Participants	Dates of data collection: July to December 1976. Setting: Naval Regional Medical Center, Portmouth, Virginia, US. Inclusion criteria: all women undergoing CS (46/122 were a repeat section). The authors' definition of primary and repeat do not correspond to definitions of elective and non‐elective used in this review (repeat sections included women in labor with ruptured membranes). The results for these 2 categories have been combined in this review. Exclusion criteria: allergy to penicillin or cephalosporin, infection or receiving antibiotics.
Interventions	Intervention: 1st generation cephalosporin: cefazolin 500 mg IV 30 minutes before and 500 mg at 2 and 1 g at 8 hrs after delivery; N = 61. Comparison: placebo: matching placebo; N = 61.
Outcomes	Endometritis (fever and uterine tenderness or fever and pathogenic organism); UTI (fever and symptoms, or positive culture); wound infection (fever, cellulitis and exudate); maternal hospital stay (treatment 5.5 days vs placebo 5.7 days, no variance given).
Notes	2 women developed serious complications as stated by the authors: 1 in treatment group developed septic pelvic thrombophlebitis; 1 given placebo developed pneumonia and endoparametritis (both included in outcome of serious morbidity). Class of antibiotic: 1st generation cephalosporin. Subgroups: both elective and non‐elective CS; before cord clamping. The 2 groups were comparable regarding age, height, weight, etc.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Randomly". Comment: no description of sequence generation process.
Allocation concealment (selection bias)	Low risk	Quote: "All preparations supplied had a code number known only by the pharmacy".
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Comment: 8 women excluded for mistakes in protocol (no further details) could not be included in ITT analysis.
Selective reporting (reporting bias)	Unclear risk	Insufficient information to judge.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Quote: "All materials appeared similar in solution". Comment: described as double‐blind, matching placebo.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: insufficient information to judge.
Other bias	Low risk	Comment: no other sources of bias identified.