Methods	Randomised controlled trial of providing feedback on cotinine to support women to stop smoking in pregnancy and reduce low birthweight Study conducted in physicians offices and clinic sites within Maine (USA) from 1984 to 1987
Participants	Inclusion criteria: Pregnant women with a singleton live pregnancy; having maternal serum AFP screening at 15-20 weeks’ gestation; who smoked >= 10 cigarettes a day Exclusion criteria: Not further specified. Recruitment: Physicians approached (no consent from women). 25,628 women completed maternal serum screening form, 97% answered question on smoking and 17% smoked >= 10 cigs/day. 2848 women were randomised (C = 1425, I = 1423) Baseline characteristics: Mean cigs/day at baseline: C = 16.3, I = 16.1 Maternal education (mean years): C = 11.8, I = 11.9. Progress+ coding: None.
Interventions	Control: Standard medical care not otherwise specified. Intervention: Report on cotinine generated for her physician with interpretation relating smoking level to birthweight. Physician explained this to the woman and also gave her a copy of the report and a pregnancy-specific booklet about how to quit, using the cotinine information also + repeat measure 1 month later, 2 copies to physician, comparison of 1st and 2nd cotinine, report commenting on the change and its interpretation Main intervention strategy: Feedback (multiple intervention) compared to usual care Intensity: Frequency (C = 0, I = 3), Duration (C = 0, I = 2). Usual care intensity: F = 0, I = 0 Intervention provided by existing staff: Effectiveness study
Outcomes	No smoking cessation data. Smoking data limited to comparability at first assessment and mean serum cotinine levels, which could not be included as they are disaggregated by low and high study site participation Mean birthweight*; low* and very low* birthweight; preterm birth* (< 37 weeks); stillbirths (> 20 weeks)*; neonatal deaths*; postneonatal deaths
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer-generated random numbers.
Allocation concealment (selection bias)	Unclear risk	Information not provided.
Incomplete outcome data (attrition bias) All outcomes	High risk	2700/2848 (94.8%) included in analysis. 3% lost to follow-up and 2% multiple gestations or fetal deaths. Only 695/1343 (48%) women in the intervention groups provided repeat serum cotinine for comparison. No ITT analysis. No smoking outcomes reported and unable to re-include data for mean cotinine and birth outcomes
Selective reporting (reporting bias)	High risk	Results difficult to interpret. Smoking cessation not recorded
Other bias	Low risk	No other bias detected.
Biochemical validation of smoking abstinence (detection bias)	High risk	Serum cotinine measurement at baseline for both the experimental and comparison groups but it was not clear that any follow-up measurements were made for the comparison group
Blinding of participants and personnel (performance bias) All outcomes	High risk	Caregivers aware of group allocation. Experimental group given feedback on serum cotinine levels
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported.
Incomplete implementation	High risk	Process evaluation showed less than good implementation with differential impact on perinatal outcome by completeness with second blood samples taken for cotinine measurement
Equal baseline characteristics in study arms	Unclear risk	Intervention groups similar at trial entry.
Contamination of control group	Low risk	Intervention not provided by care provider.