This research is a descriptive-correlational study conducted from 12 September 2022 to 5 June 2023 after the approval of the Ethics Committee of Babol University of Medical Sciences (code of ethics: IR.MUBABOL.REC.1401.148) and Lorestan University of Medical Sciences to investigate 70 married women under 18–20 years of age referring to the health centers of the city of Sepiddasht in Lorestan University of Medical Sciences who were willing to participate in the study. Based on the following formula with a confidence level of 95% and a test power of 90%, the minimum sample size was estimated at 38 people, and since the sampling method was cluster sampling, the sample size was estimated at 65 people by considering the effect size of 1.7, which with a 15% possibility of drop, it was finally estimated to be 75 people [20].
The standard normal deviate for α = Zα = 1.9600
The standard normal deviate for β = Zβ = 1.2816
C = 0.5 * ln[(1 + r)/(1-r)] = 0.5493
This research is a descriptive-correlational study conducted from 12 September 2022 to 5 June 2023 after the approval of the Ethics Committee of Babol University of Medical Sciences (code of ethics: IR.MUBABOL.REC.2022.148) and Lorestan University of Medical Sciences to investigate 70 married women under 18–20 years of age referring to the health centers of the city of Sepiddasht in Lorestan University of Medical Sciences who were willing to participate in the study. Based on the following formula with a confidence level of 95% and a test power of 90%, the minimum sample size was estimated at 38 people, and since the sampling method was cluster sampling, the sample size was estimated at 65 people by considering the effect size of 1.7, which with a 15% possibility of drop, it was finally estimated to be 75 people [20].
Measurements
The data collection tools included questionnaires on women's demographic-fertility characteristics, marital quality, sexual satisfaction, sexual self-efficacy and social support.
Demographic-fertility Characteristics questionnaire used in this study covers various aspects, including age, husband's age, menarche age, marriage age, duration of marriage, education, husband's education, BMI (Body mass index), husband' BMI, occupation, husband' occupation, residence, satisfaction with income, interval age of couple, headed status, smoking, marriage of satisfaction, number of intercourse, type of pregnancy, number of abortion, number of children and reproductive status.
Quality of Marriage Index (QMI) is a credible, valid, and global measure formulated by Norton because the mean correlation of the total items was 0.76 during the instrument development. This instrument is a six-question self-report questionnaire that measures marital quality using general phrases such as (we have a good marriage). The subject expresses his/her level of agreement in five questions of the questionnaire ranging from 1 (completely disagree) to 7 (completely agree). In the sixth question, which is a general question, the subject expresses his/her level of agreement in a range from 1 (completely disagree) to 10 (completely agree). The QMI score can range from 6 to 45, where higher scores denote greater marital satisfaction [21]. A score of ≤ 29 states relationship distress [22].
Fincham et al. reported the reliability of this questionnaire using Cronbach’s alpha of 0.96 for both male and female groups [23]. In Maroufizadeh et al.’s study, the internal consistency of this scale was calculated using Cronbach’s alpha of 0.92 [24].
Hudson’s Index of Sexual Satisfaction (ISS) was used to assess sexual satisfaction. This index is a 25-question instrument to measure the degree, intensity, or range of marital problems between couples. This scale has sufficient internal consistency (a = 0.92) and a reliability coefficient (0.76). This scale is considered a self-report questionnaire, including “I think our sexual relationships are wonderful” and “Our sexual relationships are monotonous”, rating 1 [never] to 7 (always) and ranging from 25 to 175. Higher scores indicate higher sexual satisfaction [25]. Also, in a study, the alpha coefficient for couples was higher than 0.90 [17].
In a study in Iran, the reliability coefficient of this index was calculated using Cronbach’s alpha equal to 0.97 [26]. In our study, scores < 70 were considered without sexual satisfaction, with mild sexual satisfaction, or with moderate sexual satisfaction, and scores ≥ 70 were considered high sexual satisfaction.
Sexual Self-Efficacy Questionnaire is a scale based on Schwarzer’s General Self-Efficacy Questionnaire [27], designed by Vaziri and Lotfi Kashani. This questionnaire consists of 10 multiple-choice questions scored from 0 [not at all correct] to 3 [completely correct]. The reliability of this questionnaire has been reported as 0.86 using Cronbach’s alpha, 0.81 using Spearman-Brown bisection, and 0.81 using Guttman’s method. The reliability of this questionnaire has been confirmed in Iran using content validity. The minimum and maximum possible scores are 0 and 30, respectively. Higher scores denote better sexual self-efficacy [28]. In our study, scores < 15 were considered low sexual self-efficacy, and scores ≥ 15 were considered high sexual self-efficacy.
Social Support Questionnaire (SSQ) was developed by Fleming et al. with 25 questions regarding receiving support from friends and relatives [3 questions], neighbors [4 questions], family [7 questions], society [6 questions], and ideas about social support [5 questions]. For each question, a score of 1 is considered for the positive answer, a score of 0 is considered for the negative answer, and the total score is 0–25 [29]. In a study on Iranian society, it was calculated with a Cronbach’s alpha of 0.72 [30].
Statistical analysis
SPSS software (version 20) and descriptive statistics indices (mean, standard deviation, frequency distribution table, and relative frequency) were used for data analysis, and Pearson’s correlation coefficient test was used to determine the two-way relationship (correlation).