Ershoff 1999.

Methods	3‐arm trial with individual randomisation.
Participants	Setting: ‘Between November 1996 and June 1997 in a prospective, randomised trial we recruited women initiating prenatal care at Kaiser Permanente Southern California (KPSC)’.  Inclusion criteria: 390 women. Women who had a prepregnancy smoking rate of 7 or more cigarettes per week and had not quit by recruitment, aged 18 or more, who had begun prenatal care by 26 weeks’ gestation. Exclusion criteria: reported as ‘women under the age of 18 (n = 59) and those beginning prenatal care beyond the 26th week of pregnancy (n = 69)'.
Interventions	3 study arms. Intervention focusing on smoking cessation. 1.    131 (controls) Booklet giving advice on stopping smoking. 2.    133 (booklet plus computer). Booklet with access to an interactive telephone computer programme free of charge. (Only 25 women accessed the service). 3.    126 (booklet plus motivational interviewing). Women in this group (intervention) had counselling from trained nurse educators. Counsellors were asked to complete 4‐6 calls of 10‐15 minutes duration with each woman assigned to them. Weekly calls were recommended but this was at the discretion of the nurses. For this review we have used data for groups 1 (control) and 3 (intervention) only.
Outcomes	Reported as ‘Biochemically confirmed abstinence measured by level of cotinine in urine samples obtained during a routine prenatal visit at approximately the 34th week of pregnancy.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not described.
Allocation concealment (selection bias)	Unclear risk	Not described.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Women and clinical staff delivering the intervention were not blind to group allocation although it was reported that other care providers were blind to study participation and group assignment.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical analysis for primary outcome.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Of 390 women randomised, cotinine analysis was carried out for 332 (85%). Follow‐up interview data were available for 285 women.
Selective reporting (reporting bias)	Unclear risk	The way results were reported in tables was confusing and several results were for subsamples.
Other bias	Unclear risk	No baseline imbalance apparent. Ther were considerable discrepancies between cotinine‐validated quit rates and self‐report measures.