Methods	Randomized, placebo controlled trial; 2 parallel groups.
	Unit of randomization: individual.
Participants	Dates of data collection: July-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 two categories have been combined in this review
	Exclusion criteria: allergy to penicillin or cephalosporin, infection or receiving antibiotics
Interventions	Cefazolin 500 mg IV 30 minutes before and 500 mg at 2 and 1 g at 8 hours after delivery (N = 61) vs 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: first generation cephalosporin.
	Subgroups:
	both elective and non-elective CS; before cord clamping.
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Unclear	“Randomly.”
		No further information.
Allocation concealment?	Yes	“All preparations supplied had a code number known only by the pharmacy.”
Blinding?	Yes	Described as double-blind.
All outcomes		“All materials appeared similar in solution.”
Incomplete outcome data addressed?	Unclear	No loss to follow up reported. 8 women excluded for mistakes in protocol (no further details) could not be included in ITT analysis
All outcomes
Free of selective reporting?	Unclear	Insufficient information to judge.
Free of other bias?	Unclear	The 2 groups were comparable regarding age, height, weight, etc. There was insufficient other information which to judge
Overall low risk of bias?	Unclear	Mostly unclear.