Objectives. To assess whether increases in breastfeeding initiation during the 2022 infant formula shortage persisted after formula supply normalized and whether changes differed across groups in the United States. Methods. We analyzed 2016-2024 national birth certificate data from 47 states and the District of Columbia (n = 26,789,278). Bayesian structural time-series models estimated changes in breastfeeding initiation trends, and linear probability models tested for heterogeneous effects. Results. Breastfeeding initiation remained 1.25 percentage points above pre-shortage levels during 2023- 2024 (95% credible interval [CrI], 0.58–1.77). Gains were concentrated among disadvantaged mothers: those with lower educational attainment, Medicaid coverage, or WIC participation. Racial and ethnic differences observed during the 2022 shortage did not persist. State paid family leave policies were not primary drivers of these increases. Gains were most pronounced among first-time mothers, whereas multiparous mothers experienced smaller effects. Conclusions. Breastfeeding initiation remained above pre-shortage levels, especially among mothers with fewer resources, suggesting lasting behavioral change and potential social multiplier effects that warrant consideration in policy design. However, the decline from shortage-period peaks underscores persistent structural barriers to breastfeeding.
