Sexton 1984.

Methods	Country: USA Setting: Large university hospital obstetric clinic in Baltimore, Maryland Design: Randomized controlled trial
Participants	935 pregnant women (Control 472, Intervention 463) who were smoking ≥ 10 cpd immediately prior to pregnancy, enrolled at < 18 weeks gestation. Average age 24.9 years, 40.8% Black, 59.2% White/Other, average education 12.3 years, average cpd 11.2.
Interventions	Control: not clearly specified. Intervention: at least 1 in‐person visit and additional telephone contacts from a health educator. Self‐help information was mailed every 2 weeks, and a monthly newsletter was mailed in the last year of the study. Group sessions were available. Hypnosis was offered but discontinued because of low uptake. Intervention continued until end of pregnancy. A monthly lottery ran from the first newsletter until the end of the intervention period. Participants not smoking in the previous 2 weeks entered a prize draw for a prize (e.g. perfume, makeup) worth around US$30. Participants in both groups received a US$20 gift certificate at the end of the study for participation. A bonus of a US$10 gift certificate was introduced in the last year of the study to participants 2 weeks after they stopped smoking.
Outcomes	Cessation measure not clearly stated, but recorded at 8 months gestation among women who were still pregnant. Verification used SCN.
Notes	Participants not still pregnant at 8 months were included in the study but not included in the results. Also in PIP.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated.
Allocation concealment (selection bias)	Unclear risk	Not stated.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Inadequate biochemical verification, outcome mainly based on self‐report with possible differential misreport given different levels of support in different study arms.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropout before 8 months was primarily due to early delivery or miscarriage and little difference in rate between groups.
Other bias	High risk	16% of Intervention and 17% of Control quit between recruitment and randomization which might bias effect size estimate among baseline smokers.