The present study was a randomized controlled trial. The statistical population consisted of pregnant women who visited the comprehensive health service centers of Zarinshahr (a city in central Iran) in 2019 (Figure 2).
Inclusion criteria: being in the first trimester of pregnancy, not having a urinary tract infection based on a laboratory test, not having chronic diseases such as diabetes, not taking antibiotics and immunosuppressive drugs.
Exclusion criteria: Continuous absence from training sessions (absence of more than a session during the training intervention), non-completion of the questionnaire and referral due to medical urgency (abortion, etc.).
Sampling method and calculation of sample size
Sampling was randomly conducted in accordance with the population. In Zarinshahr, there are five comprehensive health service centers from which 100 pregnant women were randomly and systematically selected according to the list of pregnant women. A computer random-number generator was used to generate the random sequence for group allocation (50 individuals in the intervention group and 50 individuals in the control group). An investigator blinded to participants selection kept the random sequence and allocated the participants to intervention and control groups at a 1:1 ratio.
The sample size was obtained equal to 44 for each group according to the following equation, and 49 individuals in each group with a 10% drop.
Z1: Confidence level of 95% was equal to 1.96.
Z2: The test power factor of 80% was equal to 0.84.
S: Estimation of the mean standard deviation of score for each variable in the two groups.
d: The minimum difference of mean scores of each variable between two groups, indicating a significant differences and was considered to be 0.6s.
Data collection method
In the study, the data collection method included a questionnaire based on constructs of theory of planned behavior. The questionnaire consisted of three parts: the first part included demographic questions, the second part included questions about knowledge, and the third part included questions about constructs of the theory of planned behavior, and included questions about attitude, abstract norms, perceived behavioral control, and behavioral intention and behavior. There were 29 questions about knowledge, designed in Yes and No, and multi-choice questions. The correct option received score 1, and wrong option was given score 0. The knowledge scores ranged from 0 to 29. For example, "Which one of cases were symptoms of the bladder infection?" About the attitude, 17 questions were designed in the questionnaire on a 5-point Likert scale from strongly agree to strongly disagree, and the scores ranged from 0 to 68. For example, "I may also have a urinary tract infection." The perceived behavioral control contained 18 questions which were scored similar to the attitude; and the scores ranged from 0 to 72. For example, "I never hold urinating, even if the frequent urination is tiresome".
Three questions were designed based on the three-point Likert scale from high to low to evaluate the subjective norms in the questionnaire. The range of scores was from 0 and 6. For example, "Spouses and other family members play significant roles in accepting the urinary tract infection prevention behavior". There were 7 questions for assessing the behavioral intention and they were designed based on a 5-point Likert scale with scores ranging from 0 to 28. For example, "I am going to consume 8 glasses of water per day."
22 questions were considered to measure the behavior in a yes/no design; the correct answer was scored 1, and the wrong answer was scored zero; and the scores ranged from 0 to 22. For example, "I always wear cotton underwear". Finally, all scores were calculated based on 100 for ease of comparison.
Validity and reliability of data collection tools
The validity and reliability of the questionnaire were proven in a study by Shamsi et al. (22). The content validity ratio and content validity index were used to assess the validity of study; and the questionnaire validity was confirmed. The internal consistency method was used to determine the reliability so that Cronbach's alpha coefficients were 0.79 for knowledge, 0.86 for attitude, 0.70 for subjective norms, 0.71 for perceived behavioral control, 0.76 for behavioral intention, and 0.81 for behavior that confirmed the reliability.
Telephone calls were made to invite women to attend the study. Five training sessions were held and designed and implemented based on the behavioral goals in order to improve the constructs of the theory of planned behavior. Table 1 presents a brief description of the training sessions (Table 1).
SPSS 20 software was used to analyze data. We used the independent t-test to analyze demographic variables (to analyze quantitative variables such as age), and Mann-Whitney test to analyze the rank qualitative variables such as education level, and Chi-square or Fisher's exact test to analyze the nominal qualitative variables such as gender. The repeated-measures analysis of variance compared the mean scores of the theory of planned behavior constructs and knowledge in each group before and after the intervention. The Kolmogorov-Smirnov test determined the data normality; and the Levene's test determined the equality of variances.
In the present study, the participants received complete information about the research purposes. They were also ensured that their information would remain confidential. The clinical trial was registered on the website of the Iranian Registry of Clinical Trials (IRCT20170214032575N1) and received a code of ethics (IR.MUI.RESEARCH.REC.1398.294) from the National Ethics Committee in the Iranian Biomedical Research (file:///C:/Users/DRshahnazi1/Downloads/4ed93mdxvizfn%20(2).pdf).