Some Japanese mothers do not follow package instructions of infant formula: a web-based analytical cross-sectional study

BACKGROUND: Not following the infant formula package instruction endangers infant health. Although infant formula misuse has been reported abroad, its incidence in Japan remains unknown. Furthermore, it is reasonable to assume that experience in childcare reduces the likelihood of making mistakes in using infant formula. This study aimed to examine the association between compliance with infant formula package instruction and childcare experience in Tokyo and surrounding prefectures in Japan. METHODS: Using a web-based questionnaire, mothers with infants were analyzed cross-sectionally and surveyed regarding their infants’ nutrition and formula preparation methods in August 2021. Compliance with the infant formula package was determined according to (a) using unlabeled infant formula, (b) preparing infant formula without reading package instructions, (c) giving formula to children ≥ 2 h after preparing, and (d) adding other ingredients to the formula bottle. The association between the misuse of infant formula and childcare experience was examined by grouping the participants by infant age (< 6 months and ≥ 6 months), and by comparing first-born child status with later-born. Of the 333 mothers with infants, 3 were excluded due to out-of-scope responses, and 330 were included in the analysis. RESULTS: The major sources of information on infant feeding methods among the participants were obstetric facilities (92.1%), internet (36.1%), and family (20.9%). The proportions of participants using infant formulas not labeled as “infant formula,” such as follow-up milk, not preparing at prescribed concentrations, feeding infant formulas > 2 h after preparation, and adding additional ingredients to the bottle were 7.9%, 4.1%, 23.1%, and 15.9%, respectively, which suggest the misuse of infant formula. These four answers did not differ significantly between mothers of children aged < 6 months and ≥ 6 months or between those with first-born and later-born children. CONCLUSION: This study suggested that some Japanese mothers do not follow package instructions of infant formula in Japan. The misuse of infant formula may not be related to the length of time spent in childcare or the presence or absence of childcare experience. Providing appropriate information on the correct use of infant formula to all caregivers, regardless of their parenting experience, is required. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s40795-022-00615-7.