The current study was an intervention type (pre-test-post-test), the study population was the smoking spouses of pregnant women who referred to health centers in Isfahan city between March and July 2019. The sample size according to a similar study [8] and considering the significance level (α = 0.05) and the power of the test (β = 80%) and the standard deviation of the second-hand smoke rejection behavior score (S = 6) And in order to achieve a significant difference in the average score of behavior in the intervention and control groups, at least 3 points, the number of 63 people and including the drop of 10%, the number of 70 people in each group was considered.

The criteria for entering the intervention include women being at least in the second trimester of pregnancy, men smoking (at least one cigarette per day around a pregnant woman), having at least third middle school education, not participating in other official educational or research programs regarding the protection against secondhand smoke, the desire of pregnant women was to continue receiving prenatal care until delivery through these health centers, and the criteria for leaving the intervention included the absence of the spouse at home for more than a week and termination of pregnancy.

The sampling method was that among the health centers of Isfahan city, 5 centers from the upper city, the lower city and the city center were randomly selected, and the number of 140 male smokers whose pregnant wives were among the clients of the health centers and other conditions of inclusion in the study had, were invited to the study, then they were randomly assigned to intervention and control groups by lottery. After completing the questionnaire and written informed consent in the pre-test phase, the training package was presented to the people of the intervention group, and two months after the intervention, the post-test was conducted. The control group, which initially received no educational intervention, received the educational package at the end of the study due to ethical considerations.

The tool used was a researcher-made questionnaire on the knowledge, attitude and behavior of smoking spouses of pregnant women, which was completed by the participants as a self-report. To determine the validity of the content quantitatively, the questionnaire was given to 10 panelists of experts in health education and health promotion, and reproductive health, and CVR = 0.87 and CVI = 0.88 were obtained, and its Cronbach's alpha reliability for the emotional dimension of attitude was 0.96. Perceived sensitivity was 0.97, perceived severity was 0.96, and behavior was 0.91.

The questionnaire created by the researcher consists of four parts: the first part demographic information: (age of men and women, education of men and women, occupation of men and women, economic status), part two: awareness 10 questions (with options yes, no and I don't know) for example (which exposure to cigarette smoke causes fetal growth, premature birth, reduction of fetal head circumference, etc.), third part: attitude in the emotional dimension 3 questions Perceived sensitivity 10 questions and Perceived severity 10 questions (on the Likert scale, completely disagree, disagree, have no opinion, agree, completely agree) for example, the attitude of the emotional dimension (I don't like smoking next to my wife, when I smoke next to my wife I feel tormented) I feel guilty…), for example, perceived sensitivity (your wife is at risk of premature birth due to exposure to cigarette smoke, your fetus will be underweight due to exposure to cigarette smoke…), for example, perceived severity (Fetal underweight due to the risk of cigarette smoke disrupts its growth, giving birth prematurely due to exposure to cigarette smoke is very dangerous and serious…) and the fourth part: Behavior 8 questions (with a Likert scale, not at all, a little), to some extent, a lot and very much) for example (not smoking around your pregnant wife, smoking in the open space of the balcony or yard away from your wife, etc.).

The educational program regarding exposure to second hand cigarette smoke was provided to the intervention group and the control group received no intervention-based program. Studying the educational package according to the busyness and time limit of the audience, including a 30–60 min educational-explanatory lecture session, educational pamphlet (made by a researcher), animation of the harms of smoking (taken from the website of the Ministry of Health), photo of a fetus (made by a researcher), SMS As a reminder, the training of pregnant women (as training assistants) was to support their husbands.

According to the different structures of the questionnaire for teaching information about pregnancy and childbirth, cigarette smoke and the diagnosis of types of cigarette smoke and its side effects for pregnancy and the fetus, there were protective recommendations against cigarette smoke, which were presented in the form of a speech to increase awareness and attitude.

Showing animation and pictures and presenting an educational pamphlet (with the content of recognizing the effects of second-hand smoke and protective strategies and reducing consumption) were used to create motivation and increase perceived sensitivity and intensity. Simple steps to quit smoking and sharing the experiences of a smoker who has quit before were used to increase performance.

In order to follow up and maintain the training, at the end of the session, a photo of the fetus was given to the participants, to be exposed to them at home, this photo was "a fetus that asked the father not to smoke". Also, men's mobile numbers were received for sending SMS reminders (at the end of every week for two months). Considering that the time interval between pre-test and post-test was two months, a reminder SMS was sent to the participants every weekend.

Pregnant women were educated to protect themselves from cigarette smoke and also support their husbands to quit smoking, and pregnant women participated in the intervention as "educational partners". The educational content is mentioned in the protocol article of this study [20].

The evaluation of the written media (educational pamphlet) was checked with several indicators, the result of the Readability Assessment of Materials (RAM) readability index was 16.6, which was at an acceptable level. The score obtained from the Suitability Assessment Materials (SAM) index was 85%, which was at an excellent level. The score obtained from the Gunning Fog reading index was 9.6, which is equivalent to the level of the third grade of middle school and was in accordance with the entry criteria. The score obtained from the index of determining the educational level of Clouse was 94%, which showed that the text is at an independent level and the learners are able to learn it without the help of the teacher and others.

Data analysis was done using SPSS 18 software, considering the normality of the data, paired t-test, independent t-test, and chi-score were used, and the significance level was considered less than 0.05. This study is the result of the PhD research thesis of health education and health promotion with code of ethics IR.SSU.SPH.REC.1396.133. All the participants were assured that the obtained information would remain confidential, and the objectives of the research were explained to them, and written informed consent was obtained. Registration of this randomized control trial has been completed with the Iranian Registry of Clinical Trials, IRCT20180722040555N1.