Methods	Quasi-RCT, 3 parallel groups.
	Unit of randomization: individual.
Participants	Dates of data collection: Jan 1979 - May 1980.
	Setting: Riverside Osteopathic Hospital, Michigan, USA.
	Inclusion criteria: women at high risk (defined as presence of labor) undergoing CS
	Exclusion criteria: oral temperature > 38° C any time prior to surgery; antibiotic use within 2 weeks prior to admission; refusal to participate; repeat elective CS; compelling indication for antibiotics in the judgement of the physician
Interventions	Either cefazolin (N = 28) 1 G IV within 1 hour prior to surgery, then 5 and 12 hours after operation for total of 3 doses, or carbenicillin (N = 34) 2G IV within 1hr prior to surgery then 6 and 12 hours after operation for a total of 3 doses or no treatment
Outcomes	Febrile morbidity (oral temperature > 38 °C twice at least 6 hours apart after the first 24 hours); wound infection (fever, cellulitis, and/or exudate); endometritis (fever, uterine tenderness and foul discharge, or fever and a positive culture with uterine tenderness and no other apparent cause); UTI (fever, urinary tract symptoms and/or positive culture >100,000 organisms/ml if pre-operative culture negative); pulmonary infection (fever with abnormal chest x-ray and/or physical signs of consolidation); undetermined (persistent fever with no discernible signs of infection)
Notes	Results of 2 antibiotic groups reported together.
	Class ofantimicrobial: first generation cephalosporin vs carboxypenicillin (carbenicillin)
	Subgroups: non-elective CS; before cord clamping.
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	No	“By random distribution of the last digit of their hospital number.”
Allocation concealment?	No	Allocation based on case record number.
Blinding?	No	No blinding.
All outcomes		Not placebo controlled.
Incomplete outcome data addressed?	Yes	No loss of participants to follow up.
All outcomes		No participant excluded after randomization.
		ITT analysis.
Free of selective reporting?	Unclear	Insufficient information to judge.
Free of other bias?	Unclear	“Lack of any significant differences between the two groups confirmed adequate randomization.”
		Insufficient other information to judge.
Overall low risk of bias?	No	Quasi-RCT give high risk of bias.