Introduction
ran’s Total Fertility Rate (TFR) declined dramatically in the past three decades [1, 2]. This trend started in the late 1980s [2] and decreased to the below-replacement level of 1.9 in 2006 [3].
The policy of encouraging more children in Iran resulted in a significant rise in TFR to 5.5 in 1988, causing a “population burst” [4]. This increase led to significant concerns about improper population growth and its consequent health problems among authorities. So the previous population policy was dropped, and low fertility was encouraged. Following this policy shift and extensive propaganda in the mass media, Iran’s TFR started to decrease, as mentioned earlier [3]. 
Recent research studies showed that despite the decrease in TFR to below-replacement levels, the ideal number of children is still two among Iranian families [5, 6]. However, single-child intention and behavior is increasing, especially in urban areas [1]. This tendency has many adverse effects for the families like less problem-solving skills, less durability, excessive sense of independence or dependence, selfishness, jealousy, seclusion, fear of losing the only child, lack of playmates, lack of family support in adulthood, impaired sense of competition, excessive relation with friends to fill the family gap and the risk of indulging in dangerous behaviors like drug addiction, and improper expectations for single-child [7, 8, 9]. 
The rapid decrease in TFR has exposed the country to imminent population challenges in the near future, so that without intervention, Iran will face population aging and decreased development indices within three to four decades [10, 11, 12]. Much research has been done to study the causes of decreased TFR in Iran [13, 14, 15, 16, 17, 18]. Social researchers have studied the reasons for single child behavior [1, 5, 19, 20, 21, 22, 23]. For example, in a study in Mashhad, the reasons for single child behavior were categorized in child-oriented (concerns about child education and related factors), and parent-oriented (parents tendency for job or study progress, concerns about the expenses of the second childbearing and associated factors) categories [24]. In another study in Tehran based on the theory of reasoned action and theory of planned behavior, different factors, including challenging experience with the first child, being too old for the second childbearing, insufficient time for the second child, motivation for job or study progress, and different personalities were recognized as underlying factors for single-child behavior [5].  
Despite the extensive research done on single-child behavior, we have not found an interventional study assessing the effectiveness of the educational intervention on childbearing intention in single-child women. However, many studies have emphasized the role of education and changing the attitudes of women about childbearing as possible solutions [23, 25, 26]. At present, childbearing consultation is done in health centers all over Iran in the form of pamphlets and face to face consultation. Still, there is no specially designed educational program, and the efficacy of the present consultations has not been evaluated.
Psychologists believe that educational programs aiming at behavioral change are only useful if they are based on health behavior theories [27]. One of the theories that have been extensively studied and shown to be effective in behavioral change is the Theory of Planned Behavior (TPB) [28, 29, 30]. This theory was introduced by Ajzen and Fishbein in the mid-1980s and tried to study human behavior in different situations using its three constructs of attitude, subjective norms, and perceived behavioral control. According to this theory, these three constructs together give rise to behavioral “intention”, which in turn will lead to actual behavior [31, 32].
Given the importance of encouraging childbearing, especially in single-child women, and taking into account the ability of TPB to explain major factors for single child behavior, the present study was designed to assess the effectiveness of education based on the theory of planned behavior on childbearing intention in single-child women.
Materials and Methods
The present study was a randomized field trial in which 72 eligible single-child women coming to Mashhad health centers from August 2019 to February 2020 were enrolled in the study.
The sample size was calculated using the effect size equation. For determining the effect size, Pakpour et al. study was used with an α error of 0.05 and 80% power [30]. For the present study, the effect size (d) was calculated using the G-Power statistical software as 1, which was readjusted to 0.7 to increase the sample size. The final sample size in each group was calculated as 33, which was increased to 37, assuming a 10% sample size drop.
The study environment included 6 community health centers randomly selected in Mashhad and the district of Torghabeh-Shandiz. At the first step, health centers number 3 and 5 were randomly drawn from the 5 main health centers of Mashhad. Then 2 community health centers from health center No. 3 and 3 centers from health center No. 5 were selected with regard to the number of daily visits and proper environment for education. One community health center was also selected from Torghabeh-Shandiz main health center. The names of the 6 selected centers were written on 6 papers and put in a bag, and then randomly drawn to put in the intervention and control groups alternately. 
The inclusion criteria were willingness to participate, being Iranian and literate, being married, having only one child aged at least 2 years and 11 months and 29 days, having no intention for the second childbearing, being 18 to 40 years old, lacking physical or psychological diseases impeding educability, the present marriage being the first marriage, lacking pregnancy contraindications as reported by woman and health center files [33], not having known fertility problems in woman or husband, and lacking major psychiatric disease as reported by woman. The exclusion criteria were the incidence of major stressful events (including the death of the husband or a close relative, severe family conflicts.) during the research period, refusing from continuing cooperation during the research period, and more than one session absence from the educational program. In the beginning, 80 women were enrolled in the study. Eight women were excluded according to exclusion criteria, and finally, data from 72 women (37 in the intervention and 35 in the control group) were examined (Figure 1).  Data collection tools included a demographic and obstetric questionnaire and researcher-designed TPB based questionnaire [1, 34] with 57 questions in 4 sections: attitude: 34, subjective norms: 10, perceived behavioral control: 10, and behavioral intention: 3 questions. A 5-point Likert-type scale (from strongly disagree to agree strongly) was used for answering the TPB questionnaire, with a score of 0 to 4 for each question. Two of the attitude questions received reverse scores.
The validity of the questionnaire was assessed with the content and face validity by 7 expert lecturers from Mashhad University of Medical Sciences. Reliability was assessed using the Cronbach alpha method and calculated as 0.85 for the whole questionnaire, 0.85 for attitude, 0.75 for subjective norms, 0.77 for perceived behavioral control, and 0.88 for behavioral intention.
After obtaining the relevant permissions, the researcher went to the selected community health centers and, after explaining the study objectives and getting written informed consent, handed the questionnaires to the participants. Then the educational program that was designed based on the TPB constructs was implemented for the intervention group, using methods of lecture giving, group discussion, question and answer, role-playing, slide show, and pamphlet distribution, during three sessions of 110 minutes duration. Education time and sessions had a wide variation among different studies [28, 29, 30, 35]. 
The educational material for this study was prepared under the supervision of expert university lecturers based on the theory of planned behavior. The researcher obtained the knowledge and skills necessary to implement the educational program under experts’ supervision. During the sampling period, whenever the number of participants from the centers allocated to the intervention group reached the threshold of 18, weekly classes were held. So the intervention group received education in two subgroups, each receiving three weekly classes, as outlined in Table 1. 


The control group received routine health centers care. The two groups were asked to fill TPB questionnaire again, once immediately after the intervention and then one month after the educational program. In previous studies, different times (from 1 month to three months) have been used to assess the change in TPB constructs [28, 29, 30, 35]. In this study, only the statistician was blinded to the allocation of the study groups. 
The study data were tested for normal distribution using the Kolmogorov-Smirnov and Shapiro-Wilk tests. The two groups were compared using the Independent t-test and the Mann-Whitney test. For inter-group testing and comparison of the three stages (before the intervention, immediately after the intervention, and one month after the intervention), Analysis of Variance (ANOVA) with repeated measures, post hoc tests of Bonferroni and Dunn, and the Freidman test were used. To assess the correlation between TPB constructs and childbearing intention before education, the Spearman rank correlation coefficient-test was used. To evaluate the role of the intervention on the improvement of childbearing intention, a Generalized Estimating Equation (GEE) model was used. The obtained data were analyzed in SPSS v. 16 at the significance level of 0.05.
Results
The mean±SD age of the participants were 32.6±4.7 and 32.9±4.7 years in the intervention and control group, respectively. The Mean±SD age of their husbands were 36.8±4.3 and 36.6±5.5, and their child Mean±SD age were 7.8±7.5 and 7.2±3.0 years in the intervention and control group, respectively. About 77.8% of the intervention and 67.6% of the control group had university-level education. The two groups were homogeneous regarding demographic data and past obstetric history (Table 2). 




The Spearman rank correlation coefficient-test showed that before the intervention, there was a statistically significant positive correlation between all three TPB constructs and childbearing intention between attitude (P=0.001, r=0.41), subjective norms (P=0.004, r=0.33), and perceived behavioral control (P=0.001, r=0.48) with childbearing intention.
The results showed that the two groups were homogeneous regarding TPB constructs before the intervention. Immediately after the educational intervention, there was no significant difference in the attitude score between groups (P=0.062). However, one month after education, the score rose significantly in the intervention compared to the control group (P=0.001). Regarding Subjective norms, there was a significant difference immediately and one month after education between the intervention and control group (P=0.009 and P=0.004, respectively). With regard to the perceived behavioral control score, the difference between the two groups was significant one month after the education (P=0.025). Regarding childbearing intention, there was a significant difference between the two groups before the intervention (P=0.001). There was also a significant difference between intervention and control group after intervention (p=0.001). Regarding attitude, within-group testing with repeated measures ANOVA showed a significant difference between different stages in the intervention group (P=0.03). Still, there was no significant change between stages in the control group. Also, the post-hoc Bonferroni test showed that the difference was significant only between one month after the intervention and before the intervention (P=0.04). Regarding subjective norms, after a significant result in repeated measures ANOVA (P=0.019), the Bonferroni test showed a significant difference between “one month after” as compared to the “before education” stage in the intervention group (P=0.037). However, repeated measures ANOVA test showed no significant difference between stages in the control group. Regarding perceived behavioral control, according to repeated measures ANOVA test no significant change was seen between the stages in either intervention or control group (P=0.142 and P=0.587 respectively). For childbearing intention, the Freidman test showed a significant difference between different stages in the intervention group (P=0.001), but there was no significant difference in the control group. Furthermore, post hoc Dunn’s test showed a significant difference between one month after the intervention and before intervention stages (P=0.001). Intra-group comparison showed that the mean score for attitude, subjective norms and intention toward childbearing did not change in the control group, while it improved significantly in the intervention group (Table 3). 


To evaluate the relationship between the TPB constructs and childbearing intention after adjusting the effect of intervention and time, a Generalized Estimating Equation (GEE) model was used and showed that change of childbearing intention score from before the intervention was significantly higher in the intervention group as compared to the control group (P=0.001). According to the GEE model, there was a statistically significant positive correlation (P<0.001) between changes in attitude score and changes in intention score (Table 4). 


Discussion 
The results of the present study showed that the childbearing intention of single-child women rose significantly after the educational intervention based on the Theory of Planned Behavior (TPB). For the three TPB constructs, the results showed that the score for attitude and subjective norms rose significantly after implementing an educational program based on TPB for single-child women, but the result for perceived behavioral control score was not conclusive.
This finding was compatible with the results of the Caplescu study in Romania that showed women with neutral attitudes were 3.6 times less likely to express an intention to have a child. In contrast, women who held a negative attitude towards childbearing were 53.6 times less likely to have such an outcome [36]. For perceived behavioral control, it was shown that using contraceptive methods had an effect on women's childbearing intention, but there were many intruding factors and the effect was not conclusive. Considering the major social and cultural differences between Romania and Iran, the results of this study cannot be readily generalized to the Iranian society and must be evaluated through domestic studies.
Regarding perceived behavioral control, it is worth mentioning that this construct is directly affected by the other two TPB constructs. Some behaviors are completely under “attitudinal” control, while others are under “normative” control. Still, others are under “perceived” control [27]. The domain of each type of control may be different in different societies. For example, certain behavior may be completely under “attitudinal” control in one community while being completely under “normative” control in another society [37]. For example, Fishbein and McLaren in a study on adults over the age of 40, showed that colonoscopy intention was completely under “normative” control, while exercise intention was under “attitudinal” and “perceived” controls [38]. 
Another reason for the failure of the educational program in changing perceived behavioral control may be the fact that despite several invitations, the husbands did not participate in the educational program. The contents of the program were handed out to husbands in the form of a booklet, but this could not compensate for their refusal to participate. Taking into account that childbearing is a complex behavior and has several aspects, many of which are not under personal control (family influences, social and cultural factors, large scale population policies, etc.), it appears that the role of these TPB constructs in childbearing intention needs to be evaluated by independent studies.
The results of the present study proved the predictive power of all three constructs of TPB for the second fertility intention in single-child women. Other studies have had conflicting results in this regard. For example, the study by Dommermuth et al. showed that fertility intention for childless women (first childbearing intention) was more strongly affected by subjective norms, while for subsequent fertilities, the roles of attitude and perceived behavioral control were more critical [39]. In Caplescu’s study, attitude and subjective norms were more significant predictors of childbearing intention, respectively [36]. Other studies have recognized several factors in the framework of TPB constructs as underlying factors for single-child intention and behavior among women [5, 19, 21]. In a study by Mobasheri et al. participants listed several factors for their decision to have only one child, including increased expenses and economic pressures, lack of government incentives and support, the attitude that “having more children is an indicator of lower social class”,husband’s objection, feeling incapable of caring for the second child, childbearing impeding job or study progress, fear of delivery, pessimistic view of relatives, and fear of miscarriage or stillbirth [21]. In another study by Behmanesh, an in-depth interview with 13 single-child women in Babol City in the north of Iran, factors like social imitation, self-priority, insecure future, and marriage conflicts were recognized as the most important factors for single-child behavior [19].
According to the present literature review, interventional studies assessing the effectiveness of the educational intervention on childbearing intention in single-child women who lacked intention for the second childbearing are limited. TPB is regarded as a comprehensive framework for educational programs aiming at health behavior changes. The results of the present study showed that educational programs based on TPB could effectively increase fertility intentions in single-child women. One of the limitations of the present study is that intention may or may not be followed by behavior because of several intruding factors [39]. Besides, personal, psychological, and cultural differences of the study units affect their responses, and this was partly controlled by the randomized allocation of study units to the intervention and control groups. Also, it must be mentioned that because of the implementation of the educational program by the researcher, blinding was not possible. 
The results of the present study showed that educational program based on TPB is effective in increasing childbearing intention in single-child women. Taking into account the worrying situation of population growth in Iran and the prevalence of single-child behavior among Iranian women, it seems that educational programs for childbearing designed upon the theory of planned behavior like the educational program of the present study can effectively increase childbearing intention among single-child women and thus help the country’s significant population policies.

Ethical Considerations
Compliance with ethical guidelines
The study subjects signed written informed consent. They also received verbal and written information about the study objectives, design, and duration. They were also reassured about their right to withdraw from the study. The confidentiality and anonymity of the subjects’ information were emphasized as well. The study protocol was approved by the Iranian National Committee for Ethics in Biomedical Research (Project Code: IR.MUMS.NURSE.REC.2019.033).

Funding
This study has been sponsored by the Research Deputy Chancellorship of Mashhad University of Medical Sciences as a thesis of the Master’s degree of Counseling in Midwifery (Project Code: 980066).

Authors' contributions
Conceptualization: Yasaman Akbarian Moghaddam, Maryam Moradi, and Mohammad Vahedian Shahroodi; Data collection: Yasaman Akbarian Moghaddam, Mohammad Vahedian Shahroodi; Data analysis: Yasaman Akbarian Moghaddam, Vahid Ghavami; Writing – original draft: Yasaman Akbarian Moghaddam, Maryam Moradi; Writing – review & editing: All authors.

Conflict of interest
The authors declared no conflict of interest.

Acknowledgements
The authors appreciate the cooperation of the involved health centers’ staff and the participating women.


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