Methods
tooth brushing behavior, abortion
 This study was a randomized controlled trial conducted on expectant mothers visiting the health centers of Arak from February to November 2022. It received approval from the Ethics Committee of Hamedan University of Medical Sciences (IR.UMSHA.REC.1399.863). In addition, this study has been approved by the Iranian Registry of Clinical Trials (identifier: IRCT20221228056955N1;  For sampling, health centers were divided according to the five districts of the municipality. Based on the size and population of each district, a few centers in each district were chosen at random (39 centers out of 50). The selected centers were randomly allocated to control (20 centers) and intervention (19 centers) groups. Eventually, the samples from each center were extracted from the Sib system via simple random sampling. Initially, 174 people were assessed to participate in the study. Nonetheless, 38 people did not meet the inclusion criteria, and 5 people were not interested in participating in the study. Moreover, 21 people did not complete the questionnaire at baseline. Accordingly, 110 people entered the study and were randomly allocated to two intervention and control groups )55 people in each group). During the study, four people in the control group (abortion = 2 and leave the group = 2) and one person in the intervention group (abortion = 1) were excluded from the study. Therefore, 54 people in the intervention group and 51 people in the control group remained for analysis (
Flowchart of Participants and Group Allocations In the present study, the data collection tool was the questionnaire used in the study by Bashirian et al, whose validity and reliability have been measured previously. The needs assessment and development of the educational program regarding the determinants of tooth brushing behavior in pregnant women were conducted based on the findings of a previous descriptive study. Before the beginning of the educational intervention, the pre-test was completed by both groups. Then, the educational program based on HPM was implemented for the intervention group through the social media application WhatsApp in the form of 9 sessions. The objectives of each session were to influence one of the constructs of the HPM. 