ProblemThe steep increase and inappropriateness of caesarean birth represent a healthcare problem in Iran. AimThe purpose of study was to evaluate the effect of a campaign based on social marketing to promote normal childbirth. MethodThe study was designed as a prospective case control study. The social marketing campaign was implemented from March 2016 to January 2017. A demographic data questionnaire, obstetrical history questionnaire, maternal knowledge assessment questionnaire, and maternal health belief questionnaire comprised the instruments for this study. Only women planning a caesarean birth without any medical indications for the caesarean were enrolled in the study as a case. Those who met the same inclusion criteria and did not want to participate in the campaign were assigned to the control group. FindingsIn total, 350 first-time pregnant women who composed the campaign group (n=194) and control group (n=156) completed the study. The mean baseline level of knowledge and Health Belief Model component score did not differ between the two groups at baseline. However, after the campaign, knowledge scores, perceived severity, perceived susceptibility, self-efficacy, and cues to action scores differed significantly between the campaign and control groups. The follow-up of all participants in both groups showed that 35.6% (n=69) of participants in the campaign group chose natural birth as their birth method, whereas only 13.5% (n=21) in the control group delivered their newborn vaginally. ConclusionThe B Butterfly social marketing campaign successfully targeted first-time pregnant women who chose to have unnecessary elective cesarean births.