Ustekinumab is usually either not detectable in breastmilk or detectable at very low levels in breastmilk. It is also likely to be partially destroyed in the infant's gastrointestinal tract and absorption by the infant is probably minimal.[1] Many infants have been safely breastfed during maternal treatment with ustekinumab. If ustekinumab is required by the mother, it is not a reason to discontinue breastfeeding and some experts and professional organizations consider it acceptable during breastfeeding.[2-8] Waiting for at least 2 weeks postpartum to resume therapy may minimize transfer to the infant.[9]