Morrison 1973.

Methods	Quasi‐RCT; 2 parallel groups. Unit of randomization: individual.
Participants	Dates of data collection: not reported. Setting: City of Memphis Hospitals, Tennessee; indigent women, many obstetric and metabolic complications. Inclusion criteria: all women undergoing CS. N = 330. Exclusion criteria: febrile or infected.
Interventions	Intervention: drug combination [penicillin + aminoglycoside]: aqueous penicillin 10 MU every 8 hrs and kanamycin 500 mg IM every 12 hrs pre‐operatively and for 3 days post‐operatively; N = 115. Comparison: no treatment: no treatment; N = 115.
Outcomes	Fever (> 100.9oF after 2nd post‐operative day), severe pelvic infection (treatment 27% vs control 7%); 'free of infectious morbidity' (3.6 vs 6.8 days); maternal hospital stay (5.4 vs 8.8 days, no variance given).
Notes	No adverse drug reactions reported; no evidence of development of resistance reported. Unable to ascertain from description of study incidence of endometritis or wound infection; inadequate description of nature of severe pelvic infections (not included as outcome in analysis). 2 groups of women were studied retrospectively (N = 75); methods nor results do not specifically describe results of this group and it is unclear whether they have been included in the overall results. Class of antibiotic: aminoglycoside‐containing combination (natural penicillin and aminoglycoside. Subgroups: type of CS unclear; before cord clamping. The 2 groups were comparable regarding gravidity, parity, age and operative indicators.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote: "...every other patient". Comment: quasi‐RCT. Alternate allocation to treatment or no treatment.
Allocation concealment (selection bias)	Unclear risk	Comment: no information provided.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: no loss to follow‐up; no participants excluded. ITT analysis.
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.