The research data were collected from 455 mothers admitted to the postpartum and lactation unit of a city hospital in Istanbul between September and November 2022. The mothers to be included in the study sample were determined according to the non-probability sampling method, considering the inclusion criteria of the study. The research data were collected by the researchers face-to-face through a questionnaire that lasted about 10-20 minutes.

The form prepared by the researchers consists of 25 questions containing information about the mother, the infant, and the nutrition characteristics.

The BMEE, which was developed to determine the breast milk expression experience of mothers, consists of 11 items. The BMEE is a five-point Likert type, ranging from one (strongly disagree) to five (strongly agree). It has three sub-dimensions: social support, learning experience, and personal experience. When the mean of the total items' score is less than three, the breast milk expression experience of the mothers is evaluated as negative.

The scale was designed to evaluate women's attitudes towards breastfeeding and predict the duration of breastfeeding as well as the choice of infant feeding method. IIFAS consists of 17 items and is a five-point Likert type (one-strongly disagree to five-strongly agree). While nine items of the IIFAS contain positive attitudes about breastfeeding, the other eight items contain positive attitudes about formula feeding. The total IIFAS score can range from 17 to 85, with higher scores reflecting a positive attitude towards breastfeeding. Total IIFAS scores can be categorized into three groups: positive to breastfeeding (IIFAS score 70-85), neutral (IIFAS score 49-69), and positive to formula feeding (IIFAS score 17-48).

MSPSS subjectively assesses the adequacy of social support from three different sources (family, friends, and a significant other), consists of 12 items, and is a seven-point Likert type (one-very strongly disagree to seven-very strongly agree). The lowest score to be obtained from MSPSS is 12, and the highest score is 84. The higher the total score, the higher the perceived social support.