RecruitingBehavioural interventionPrevention of Postpartum Smoking Relapse and Related Health Consequences by Breastfeeding PromotionThe objective of this randomized controlled trial is to examine the efficacy of a new intervention to prevent postpartum smoking relapse and related health consequences through breastfeeding promotion. After the pre-test, ex-smokers who are still abstinent from smoking will be randomized into either the breastfeeding intervention or the attention placebo control group. The outcomes are postpartum smoking relapse, breastfeeding practices, and maternal and child health.