Breastfeeding is associated with well-known benefits including reduced risk of asthma, obesity, and early-life infections for children and lower risk of breast and ovarian cancers, Type 2 diabetes, and high pressure for the lactating parent (Centers for Disease Control and Prevention, 2023a; Meek and Noble, 2022). Up until 2022, exclusive breastfeeding was recommended until at least six months of age, and breastfeeding along with solid foods up to one year of age or beyond. This recommendation is now two years or longer per the World Health Organization Guidelines, American Academy of Pediatrics (AAP), and other agencies (Meek and Noble, 2022). Yet, only about one-third of mothers in the United States continue breastfeeding until 12 months (National Immunization Survey 2022). This is likely because of several known barriers, including sociocultural, medical, nutritional, and infant-level factors, ranging from issues with breastmilk supply and latching to competing responsibilities for work and family (Teich et al., 2014).

Aside from these known barriers, endocrine-active chemicals can interfere with hormonal mechanisms that regulate both the initiation of breastfeeding and sustained milk production (Abbott, 2009; Criswell et al., 2020). These chemicals include certain per- and polyfluoroalkyl substances (PFAS), which in experimental studies disrupt mammary gland differentiation (Tucker et al., 2015; White et al., 2007; Yang et al., 2009), interfere with placental hormones, or alter expression of genes encoding milk proteins and, by extension, milk composition (Criswell et al., 2020; Suh et al., 2011; White et al., 2007). Prior studies suggest that PFAS may decrease breastfeeding duration (Fei et al., 2010; Nielsen et al., 2022; Rokoff et al., 2023; Romano et al., 2016; Timmermann et al., 2022). For instance, greater maternal blood serum or plasma concentrations of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) during pregnancy have been associated with shorter duration of breastfeeding in multiple studies (Fei et al., 2010; Rokoff et al., 2023; Romano et al., 2016; Timmermann et al., 2017, 2022); an additional study reported similar associations when using residential address before delivery as a proxy for exposure to PFAS-contaminated water (Nielsen et al., 2022). In contrast, a large study from Norway reported a decreased risk of early cessation of breastfeeding with certain PFAS (perfluorononanoate (PFNA), perfluorodecanoate (PFDA), perfluoroundecanoate (PFUnDA)), and no association with PFOA and PFOS, which were observed at lower concentrations than most prior studies (Rosen et al., 2018). Similarly lower concentrations observed in a later U.S. study observed no association of PFAS with breastfeeding duration among primipara (Friedman et al., 2023). Few prior studies have examined influence of PFAS mixtures on breastfeeding duration (Friedman et al., 2023; Rokoff et al., 2023), and the majority of studies have been from Europe (Fei et al., 2010; Nielsen et al., 2022; Rosen et al., 2018; Timmermann et al., 2017, 2022) with fewer studies from North America (Friedman et al., 2023; Rokoff et al., 2023; Romano et al., 2016). To expand and strengthen these areas of research, we examined the potential effects of PFAS mixtures on duration of breastfeeding in a population of rural pregnant people recruited from prenatal clinics in New Hampshire, USA.