Systemic lupus erythematosus has been linked to excess preeclampsia in pregnancy and preterm delivery, however promising preliminary data suggest that hydroxychloroquine may protect pregnant women with lupus from these potentially catastrophic outcomes. This work leverages three large population-based databases from around the world (United States, Israel, and Sweden) with detailed prescription and clinical data to address threats to internal validity common in pharmacoepidemiological studies such as confounding by indication and selection bias while disentangling these outcomes from the effects of potential mediators such as glucocorticoids and gestational diabetes. Finally, given that hydroxychloroquine is safe and effective in pregnant women with lupus for managing their disease, we will work with patients and providers to understand why pregnant women with lupus are either choosing not to use this medication or are not being prescribed it in the first place.