Study design and sample
A descriptive and correlational design has been used in this study. The population of the study comprised all the pregnant women applying to the obstetrics polyclinic of a university hospital. No study was observed which investigated the effects of independent variables on the prenatal breastfeeding self-efficacy of pregnant women, which is regarded to be the primary result of this study, and as such, no results were obtained which could be used in the sample calculation. Having predicted the effect of independent variables on pregnant women’s prenatal breastfeeding self-efficacy scale scores to be f2: .08 (small effect) based on the multiple regression analysis results, it was determined that at least 285 pregnant women should participate in the study as per the sample number calculation done on the G*Power (3.1.9.2) software with 5% alpha margin of error (two-sided) and 90% power. Taking into account the possibility of losses to occur during the data collection process, it was decided that 314 pregnant women would participate in the study, 10% more than the number found in the sample number calculation. Based on the value of R2: .25 obtained from the regression analysis which determined seven independent variables to have an effect on pregnant women’s prenatal breastfeeding self-efficacy scores, regarded to be the primary result of this study, the effect size and the power were found to be f2: .33 (medium effect) and 1.00 (100%) respectively in the post hoc power analysis done on the G*Power (3.1.9.2) software, and the sample number of the study was determined to be sufficient. The study was conducted in a random sampling design, one of the non-probability sampling methods, choosing among pregnant women applying to the obstetrics polyclinic of a university hospital. Pregnant women who were in their third trimester (27th pregnancy week and above), had a single and healthy fetus, had a spontaneous pregnancy and had no health problems were included in the study.