2.6.1. Demographics

Age was coded as 15 to 17, 18 to 34, and 35 and over. Race/ethnicity was coded as non-Hispanic White, and Other.

#### 2.6.2. Breastfeeding

"Breastfeeding initiation" was based on three questions including: (1) declared breastfeeding status (currently breastfeeding, previously breastfed, planning to breastfeed, or never breastfed); (2) "One week after you gave birth, how were you feeding your baby?", with responses of breast

milk only, formula only, both breast milk and formula; and (3) "How old was your baby when you stopped breastfeeding completely?", with responses of one through thirteen months or baby has not stopped breastfeeding. Ever having breastfed was defined as reporting currently breastfed, previously breastfed, feeding breast milk one week after birth (only or in combination with formula), having stopped breastfeeding, or having a baby that has not stopped breastfeeding. Never having breastfed was defined as reporting planning to breastfeed, never having breastfed, not feeding with breast milk the first week after birth, not having stopped breastfeeding, and not having a baby that continues to breastfeed.

"Duration of breastfeeding" was based on the declared breastfeeding status and the question: "How old was your baby when you stopped breastfeeding completely?" (see "Breastfeeding initiation" for all response categories). Breastfeeding for less than 4 months was defined conditionally on having reported previously breastfeeding and having stopped breastfeeding after one, two, or three months. Breastfeeding for greater than or equal to 4 months was defined conditionally on having reported previously breastfeeding and having stopped breastfeeding after four or months.

"Reason for stopping breastfeeding" was based on the question: "What were your reasons for stopping breastfeeding?" Responses were categorized as physiological (difficulty nursing or latching; not enough milk, milk dried up; too painful, too hard, nipples too sore; I got sick, my baby got sick, had to stop for medical reasons), other commitments (too much time, I went back to school, I went back to work), and met goal (I met my goal). More than one reason could be reported.

## 2.6.3. Employment and Industry

"Employment status" was based on the question: "What is your employment status?" Responses were categorized as full-time, part-time, and other. Other included individuals not in the labor force, unemployed, in school, disabled, seasonal workers, and/or stay at home mothers.

"Industry" was coded according to 2012 Census Industry Classification Codes. Industry responses were combined into broader categories to increase the number of responses in those categories for analysis purposes. "Accommodation, food, and hospitality" included responses from women working in restaurant, travel and hotel jobs. "Healthcare" included women working in healthcare or in a hospital setting as well as working in home healthcare, as a licensed nursing assistant, or in an assisted living or nursing home environment. "Retail" included women working in grocery, clothing, convenience, and department stores. "Other" included all other industries with sample sizes too small to consider separately. This included but was not limited to education, social assistance services, manufacturing, and other services. Study participants were asked to respond to the industry question only if they were currently employed or planning to return to work.
