Figure 1. Flow of participants through the study.

“Active refusal” indicates potential participants who were contacted but declined to participate. “Passive refusal” indicates potential participants with whom contact was not possible. Once randomized, self-reported smoking status was assessed by telephone interview 7 weeks after randomization, at 38-weeks gestational age, and at 3-months postpartum. At each timepoint, “delivered” indicates participants who delivered prior to the time of assessment; “unable to contact within window” indicates participants who were not reachable by phone within the 3-week window allowed for contact; “withdrew” indicates participants who refused further participation in surveys; “declined survey” indicates participants who declined to respond to the phone interview at that point in time but indicated willingness to be contacted in the future; and “withdrew” indicates participants who both refused to participate and did not wish to be contacted at future timepoints.