Ng 1992.

Methods	RCT; 3 parallel groups. Unit of randomization: individual.
Participants	Dates of data collection: March to August 1991. Setting: Ipoh, Malaysia. Inclusion criteria: women undergoing CS. N = 222. Exclusions: hypersensitivity to 1 of antibiotics; presence of infection or fever; on antibiotics; multiple pregnancy.
Interventions	Intervention: 3rd generation cephalosporin: cefoperazone 1 g every 12 hrs x 3; N = 71. Intervention: ampicillin 500 mg every 6 hrs x 4; N = 74. Comparison: no treatment: no treatment; N = 77. At induction of anesthesia. Control data split to 6/35 and 5/35 for comparison with penicillin and cephalosporin respectively.
Outcomes	Wound infection (inflammation over wound with serous or purulent discharge); any antibiotics post‐operatively (cefoperazone vs ampicillin vs no treatment: 6.6% vs 16.2% vs 25.7%). Hospital stay: ampicillin vs no treatment 5.57 days (SD 1.43) vs 6.5 days (SD 3.67).
Notes	Author's definition of emergency not consistent with criteria used in this review; classified as both/undefined. Class of antibiotic: 3rd generation cephalosporin or aminopenicillin (ampicillin). Subgroups: type of CS unclear; before cord clamping. The 3 groups were comparable regarding age, race, parity, gestational age, etc. The number of patients allocated to the control and cefoperazone group are different between the text and the table; the numbers in the text have been used.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "...randomized..". 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	2 patients excluded (1 from cefoperazone group, 1 from no treatment group); as‐treated analysis performed.
Selective reporting (reporting bias)	Unclear risk	Comment: insufficient information to judge.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: no blinding; not placebo‐controlled.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Comment: probably outcome assessment was not blinded.
Other bias	Low risk	Comment: no other sources of bias identified.