OBJECTIVE: Despite American Academy of Pediatrics recommendations, some parents refuse intramuscular (IM) vitamin K as prophylaxis against vitamin K deficiency bleeding for their newborns. The purpose of our study was to describe attitudes and perceptions of parents who choose to defer IM vitamin K for their newborns. METHODS: Using qualitative methodology, we conducted in-depth semi-structured interviews with parents of newborns in 3 hospitals in Connecticut and California. We used the grounded theory approach and the constant comparative method until saturation was reached. RESULTS: Nineteen participants (17 mothers and 2 fathers) of 17 newborns were interviewed; 14 newborns did not receive IM vitamin K due to refusal by the parents, and for 3 newborns IM vitamin K administration was delayed due to initial hesitation by the parents. Four major themes emerged: 1) risk-to-benefit ratio, where parents refused IM vitamin K due to a perceived risk to their newborn from preservatives, for example; 2) "natural" approaches, which led to seeking oral vitamin K or increasing the mother's own prenatal dietary vitamin K intake; 3) placement of trust and mistrust, which involved mistrust of the medical and pharmaceutical community with overlapping concerns about vaccines and trust of self, like-minded allopathic and nonallopathic health care providers, the social circle, the internet, and social media; and 4) informed by experiences, reflecting hospital experiences with prior pregnancies and communication with health care providers. CONCLUSIONS: Parents' perception of risk, preference for alternative options, trust, and communication with health care providers were pivotal factors when making decisions about IM vitamin K.