Infant and young child feeding is crucial to physical and mental development and long-term health. In developing settings, the widespread use of formula raises concerns regarding the growth and development of infants. However, little is known about the role that formula may play in the observed poor infant health, nutrition and development in developing areas. Using a rich panel dataset of 1,802 infants aged 6-30 months collected at six months intervals from rural China, we describe the prevalence of formula feeding, identify households that are more likely to use formula, and examine the associations between formula feeding with various dimensions of infant health, nutrition and development outcomes: anthropometric measurements, infant illnesses, cognitive, psychomotor, and socio-emotional development. We found infant formula is widely used in rural China, and it is significantly associated with infant health and nutritional outcomes - formula feeding is associated with a 4.59-point increase in Hemoglobin concentration and a 13% reduction in anemia prevalence, but is also associated with a 0.11-sd decrease in weight-for-age and height-for-age Z-scores. Moreover, infants are more likely to be fed formula when their families have higher socioeconomic status, when their parents have out-migrated, and when they have no siblings. Our findings suggest that there is a need to promote age-appropriate feeding practices, with an emphasis on families who are particularly in need of guidance, to reduce over-reliance on formula, and provide support for mothers to delay their migration or create pathways for rural parents to bring their children with them when they migrate
