RecruitingPhase 4Drug trialProspective Registry Investigating Maternal, Infant, and Lactation Outcomes in Anifrolumab UsersProspective Registry Investigating Maternal, Infant, and Lactation Outcomes in Anifrolumab Users (PRIMULA Lac) is a Post Marketing Requirements (PMR) study designed to fulfill the FDA post-marketing requirements. The study will collect data about the presence of anifrolumab in human breast milk and serum (maternal and infant) among lactating individuals who are receiving anifrolumab therapeutically via intravenous (IV) or subcutaneous (SC) administration and evaluate exposure and effects on the breastfed infant.