Lillington 1995.

Methods	Country: USA Setting: 4 women, infant and children sites in south‐central Los Angeles, California Design: cluster‐RCT
Participants	768 pregnant women, 18+, who had smoked in the previous year, attending any of 4 clinic sites (2 experimental, 2 control) from similar neighbourhoods that were paired on ethnic mix. Of 555 women followed up, average age 26.8 years, 291 (53.0%) African‐American, 234 (42.6%) Hispanic, 20 (3.6%) Caucasian, 4 (0.7) Other ethnicity, 225 (40.5%) current smokers and 330 (59.5%) ex‐smokers at baseline. Participants in experimental group were more likely to be current smokers (51.0% versus 36.5%) and less likely to be in 3rd trimester (22.1% versus 39.5%) than controls.
Interventions	Experimental group: assessment of smoking motivation and intention to quit. Bilingual (Spanish/English) health educators provided 15 minutes individual counselling including risk information and quit messages or reinforcement. Participants selected a quit date and nominated a “quit buddy”. Participants received a self‐help guide (“Time for a change”) with behavioural counselling. Weekly prize draws were available for completing activity sheets. Prizes were inexpensive baby items (e.g. baby toys, infant clothing) and a grand prize of US$100. Participants received a booster postcard after 1 month. Control group: “Usual care”, including printed information about the risks of smoking during pregnancy and a group quit‐smoking message.
Outcomes	PPA at 6 weeks postpartum (self‐report + salivary cotinine < 20 ng/mL, although majority of self‐reported quitters did not provide a saliva sample).
Notes	Study sample contains both current smokers and ex‐smokers at baseline. Length of follow‐up differs between participants, depending on length of gestation at time of recruitment. 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	Only 111/254 of those who self‐reported smoking provided a saliva sample, and quote: “the number of saliva samples was too small to permit analysis for the baseline smokers”.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Overall 28% attrition in intervention group and 25% in control group, combining both baseline smokers and ex‐smokers. Attrition not reported separately for baseline smokers.
Other bias	High risk	Analysis did not allow for clustering or matching of clusters. Baseline inequality in important characteristics such as % currently smoking.