In their article titled "Hospital Infant Formula Discharge Packages: Do They Affect the Duration of Breast-feeding"? Dungy et al1 claims that including infant formula in hospital discharge packages does not decrease the duration of breast-feeding. In this study, each of the intervention groups and the control group had an equivalent 17% rate of exclusive breast-feeding at 16 weeks.
Donnelly BW. Formula Discharge Packages' Effect on Breast-feeding Duration. Arch Pediatr Adolesc Med. 1998;152(1):102. doi: