Associations Between Infant Formula Exposure, Housing Instability and Postneonatal Mortality Among Participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC).

Objectives: To quantify infant mortality rates (IMR) using expanded racial categories, and to examine associations between infant formula exposure, housing instability and postneonatal mortality among Minnesota WIC Participants.

Methods: Births in Minnesota from 2014 through 2019 (n = 404,102) and associated infant death records (n = 2034) were used to calculate neonatal and postneonatal rates using expanded racial categories. Those births that participated in the WIC program (n = 170,011) and their linked death records (n = 853) were analyzed using logistic regression to examine associations between formula exposure, housing instability, and postneonatal death.

Results: Postneonatal IMR was more than twice as prevalent among Black (African American) as East African immigrant infants (IMR = 3.9 vs 1.5). After adjustment for confounding (term status and nativity of mother (U.S. vs foreign born), infants exposed to formula by 28 days were four times as likely to die in the postneonatal period as those without formula exposure (aOR = 4.0; 95% CI 3.2-4.9). WIC participants who experienced housing instability at birth were 1.7 times as likely to lose an infant in the postneonatal period (28 to 364 days of age) as those in stable housing (aOR = 1.7; 95% CI 1.2, 2.4).

Conclusions for practice: Disaggregating Black mortality rates revealed inequities in infant mortality among Black families of varied backgrounds. Formula exposure and housing instability are modifiable risk factors associated with postneonatal mortality. Appropriate interventions to reduce barriers to breastfeeding and provide housing stability for vulnerable families could reduce disparities in postneonatal mortality.