**1. Introduction**

Over the last two decades, the global public health community established that working outside the home was negatively associated with breastfeeding [1–4]. The World Health Organization has recently recognized the need for increased supports to improve breastfeeding duration and initiation rates, recommending women breastfeed for two years [5]. However, research in the United States (U.S.) found only 49% of women breastfeed for 6 months and breastfeeding initiation was impacted by working or planning to work postpartum [1,3,6,7]. Studies have found that breastfeeding incidence and duration were lower among employed, working-age women [1,3,8–10].

Moreover, women planning to work full-time postpartum were less likely to initiate breastfeeding than women who planned to work part-time and women were more likely to cease breastfeeding the first month prior or subsequent to returning to work [1,4]. Employment was also associated with breastfeeding less than two to three months postpartum [2]. Women who return to full-time employment six to twelve weeks postpartum were more than 50% less likely to meet their breastfeeding intentions, and women who return to full-time employment less than 6 weeks postpartum were more than twice as likely to not meet their breastfeeding intentions, compared to women who do not work [11].

Having identified this disparity, recent research has recognized the need to explore factors that influence breastfeeding cessation when returning to work [12]. Mothers themselves report multiple barriers to breastfeeding once returning to work, such as a lack of flexibility in the work schedule to allow for milk expression; lack of accommodations to express and/or store human milk; and concerns about support from supervisors and colleagues [13,14]. A woman's breastfeeding duration is also influenced by the existence and quality of maternity leave including its length, paid or unpaid status, and the attitudes, policies, and practices at her place of employment [15]. Among working women or women returning to work, research has found breastfeeding initiation and duration were lower for low-income women and women with less than a high school education [4,11]. However, this literature does not characterize specific, practical worksite factors that influence breastfeeding disparities among vulnerable populations.

#### *1.1. Special Supplemental Nutrition Program for Women, Infants, and Children*

Breastfeeding disparities experienced by low-income women due to individual, social, and environmental barriers are well documented [5,16]. Breastfeeding prevalence among low-income women, specifically women enrolled in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), continues to be below national targets established in Healthy People 2020 [17]. Nationally, WIC mothers have lower rates of breastfeeding than non-participants, despite WIC's efforts to encourage breastfeeding through the Loving Support Makes Breastfeeding Work campaign and the WIC Peer Counseling Program [18–20]. Among WIC participants, barriers to breastfeeding include embarrassment toward breastfeeding in public, early return to work or school, infant behavior, lactation complications, lack of self-efficacy, low income, limited social support, less education, and unsupportive childcare [21–24].

The type of employment generally obtained by WIC eligible mothers further contributes to the disparities found in the U.S. WIC eligible mothers are more likely to have low-income jobs in childcare, home healthcare, or in one of the service industries [25]. These jobs are less likely to have flexible schedules or have paid-for breaks to express breast milk, both of which contribute to the mothers decision-making about continuing to breastfeed or early weaning [16]. These industries also usually lack workplace lactation policies and supports, which influence a woman's choice to continue breastfeeding upon returning to work [12].

The studies among WIC mothers identify a vulnerable population at risk of experiencing disparities in breastfeeding, which vary by employment type. However, employment supports and policies for breastfeeding are geographically and industry-dependent. For example, in New Hampshire (NH), according to the 2016 NH WIC Pediatric Nutrition Surveillance data, 76.8% of WIC mothers initiate breastfeeding after delivery, compared to 87.4% of all mothers in New Hampshire [26,27]. Further, previous studies have found that NH WIC mothers are less likely to have ever breastfed than other mothers in the U.S. or NH, and WIC mothers' breastfeeding duration was significantly related to employment status [21,28]. Additional state-specific research is needed to better understand and characterize breastfeeding disparities across employment types among WIC mothers.
