The BE CARING Study is taking place to gather information on bimekizumab in the breast milk of mothers who are breastfeeding and taking bimekizumab. This study will also look at the levels of bimekizumab in the blood of both the mother and her breastfeeding baby. The information that researchers learn in this study might be able to help other women in the future who are facing the difficult decision of whether to take bimekizumab while they are breastfeeding.