A Study to Measure Mirikizumab Levels in Breast Milk of Lactating Participants Receiving Mirikizumab Therapeutically for an Approved Indication

Inclusion Criteria: Study Participants: * Mothers who are at minimum 18 years of age and their infants who are at least 36 weeks gestation age at birth and at least 3 weeks old by Study Day 0 * Multiple births may be allowed following discussion with the medical monitor. Note: in the opinion of the healthcare practitioner (HCP), there are no infant or maternal issues that would preclude the mother participant or the infant from participation * Lactation history is well established, with the mother exclusively breastfeeding her infant * Mother participant is receiving mirikizumab therapeutically for an approved diagnosis (having received at least 2 doses of mirikizumab SC maintenance therapy every 4 weeks prior to study Day 0) * Have a breastfed infant who can feed from a bottle with previously stored breast milk or formula Exclusion Criteria: * Have a history of inadequate lactation, for multiparous participants who have previously breastfed * Have a significant previous or current history of comorbidities capable of significantly altering the absorption, metabolism, or elimination of drugs, or of constituting a risk when taking mirikizumab, or of interfering with the interpretation of data * Have any condition that fulfills any contraindication stated in the label. All warnings and precautions stated in the label need to be considered * Have a history of breast augmentation procedures judged to have a clinical impact on breast milk expression such as breast reduction s…