Study design

A cluster randomized controlled trial will be carried out on breastfeeding mothers referred to health centers affiliated to Tehran University of Medical Sciences. A cluster randomized controlled trial design was chosen because it makes it easier for mothers to attend classes at their local health center, and in this design, the phenomenon of contamination between the intervention and control groups is avoided. Besides, it can help us increase the representativeness and generalizability of our study population and results. The control group allows us to analyze the direct effect of the intervention and discount an increase in milk donation due to other factors [20]. This study was approved by the Research Ethics Committees of School of Nursing and Midwifery & Rehabilitation - Tehran University of Medical Sciences (IR.TUMS.FNM.REC.1401.150).

Setting

This study will be conducted in health centers affiliated to Tehran University of Medical Sciences. Tehran University of Medical Sciences covers primary health care services of 5 out of 22 districts of Tehran City (district numbers 10, 11, 16, 17 and 19) [21]. These health centers were chosen because they cover a significant portion of breastfeeding mothers of South Tehran, who usually bring their infants to theses\ health centers for vaccination, screening or growth monitoring. However, we will include four of these districts in our study (district numbers 10, 11, 16 and 17) because the health centers of district number 19 do not have the equipment for holding in-person classes and the population of Iranian breastfeeding mothers in that district is limited. These four districts have a total of 20 health centers. From among all these health centers, we will choose eight centers using simple randomization method; then, a cluster of four centers will be randomly selected for collecting the intervention group and four centers for collecting the control group. We will recruit eight to nine participants from each health center.

Recruitment

Eligibility for the study is as follows: being breastfeeding mothers who are within one year after giving birth and have sufficient breast milk for their own baby, with the approval of a doctor or midwife, having no serious medical condition (both mother and infant), and being a resident of Tehran.

The exclusion criteria are: breastfeeding cessation, loss of baby, not participating in more than one session of educational program, and not responding to more than 20% of the questionnaire.

Breastfeeding mothers who meet the inclusion criteria will be selected by convenience sampling, and they will be approached to explain the study aims, risks and benefits in a way that is easily understood. If they give permission to participate in study, they will provide written informed consent, then they will fill out the pretest questionnaire in order to obtain the baseline assessment.

Sample size

In order to provide a power of 95% with 95% confidence interval the following formula and the standard deviation of 3.17 to 3.21 (according to the same study’s findings) will be used [18]. The sample size was estimated at 30, and then allowing for 10% attrition, we plan to recruit 33 samples per group and a total of 66 study participants.

$$ n=\frac_}+_\right)}^\left(_^+_^\right)}}_-}_\right)}^}$$

$$ \frac^\left(^+^\right)}^}=29.4\cong 30$$

$$ 30+30\left(0.1\right)=33$$

Development of the educational intervention

In this study, the educational intervention is designed by reviewing literature comprising guidelines and statements on donor milk, human milk bank, storage and preparation of breast milk and the importance of breast milk from the following sources: Human Milk Banking Association of North America (HMBANA), European Milk Bank Association (EMBA), World Health Organization (WHO), United Nations Children’s Fund (UNICEF), Centers for Disease Control and Prevention (CDC), and American Academy of Pediatrics (AAP) [22,23,24]. We also used the Human Milk Bank Clinical Guideline in Iran, which covers various aspects such as the infrastructure, awareness, communication, ethical issues, donors, recipients, and working processes of a human milk bank [25].

After that, we applied the Delphi method to gather and validate the material according to the opinions of experts in midwifery and reproductive health and neonatology of Tehran University of Medical Sciences. We conducted three rounds of questionnaires with the panel, which consisted of three neonatologists, three midwives who have experience in breastfeeding education, one health education professional, and one midwife who was in charge of a milk bank. They were well informed and familiar with the Iranian culture and community, especially regarding the issues of milk kinship and the role of the husband and families in Iranian mothers’ milk donation, and breastfeeding mothers’ skills and self-efficacy in expressing their breast milk.

Intervention design

Following baseline data collection, the intervention group will start receiving 60-minute weekly educational intervention based on TPB components for four weeks (Table 1).

Table 1 The content of the educational sessions based on the theory of planned behavior

Lectures, small groups discussion, educational pamphlets and booklet, PowerPoint presentations, showing videos and pictures, will be the main educational methods and materials that we are going to use in order to make the program effective and interesting. Moreover, we will ask mothers to share the booklet and pamphlets with their family and friends. Sessions will be held in health centers for the intervention group while the control group will receive only usual education.

Data collection

The questionnaire will be uploaded to Porsline, a well-known online survey platform in Iran, to create a link for the questionnaire. Participants can use their mobile phones to open the link and fill out the questionnaire. A baseline assessment will be conducted prior to the intervention for both the intervention and control groups. In order to assess the immediate and long-term effects of the intervention prospectively, the first follow up assessment will be conducted immediately after the intervention, and the final one will be conducted 12 weeks later. Our primary outcomes are the number of mothers who have donated their breast milk and changes that have happened in breastfeeding mothers’ knowledge, attitudes, subjective norms, perceived behavioral control about DHM and intention to donate milk. Our secondary outcomes are the associations of behavioral determinants and social demographic variables with milk donation.

Development of the measurement tool

Data will be measured by a 46-item researcher-made questionnaire. This instrument has been created by reviewing literature on milk donation and previous studies on TPB and consists of seven sections as described in Table 2.

Table 2 Theory of planned behavior-based survey questions

Theory of planned behavior assumes that individuals’ behavior is directly determined by three main components, namely: attitude, subjective norms, and perceived behavioral control [18, 19].

Behavior: the action of donating breast milk.

Intention: perceived likelihood of donating breast milk.

Attitude: favorable or unfavorable perceptions of donating breast milk which are determined by breastfeeding mothers’ knowledge, beliefs, and experiences.

Subjective norms: beliefs about whether most people who are important to breastfeeding mothers approve or disapprove of donating breast milk.

Perceived behavioral control: breastfeeding mothers’ perceptions of the ease or difficulty of donating breast milk.

The reliability of questions will be checked for internal consistency (Cronbach’s alpha) and the content validity of the questionnaire will be assessed by both qualitative and quantitative methods. In the qualitative method, ten experts in breastfeeding and the health promotion field will assess questioners. The experts include Faculty members of the Midwifery and Reproductive Health Department and neonatologists of Tehran University of Medical Sciences, and, after receiving their opinions, any required modification will be made. In the quantitative method, content validity index (CVI) and content validity ratio (CVR) will be measured. For face validity we will ask ten breastfeeding mothers to provide feedback on the clarity of the questionnaire and based on their opinions some essential clarification will be made.

Statistical analysis

We will use descriptive analysis to report baseline characteristics. In this study the Repeated ANOVA between subjects test will be used for quantitative variables which have a normal distribution, and the Friedman test will be used for quantitative variables that do not have a normal distribution. For qualitative variables, chi-square test or Fisher’s exact test will be used. The effectiveness of the intervention will be assessed using the repeated measure ANOVA test and the effect of demographic variables on milk donation behavior will be determined using a logistic regression model. Statistical analyses will be made using IBM-SPSS 22. The trial has been registered at the Iranian Registry of Clinical Trials (IRCT20230124057203N1).