Prescription drugs are widely used in pregnancy, particularly to manage chronic conditions. However, since randomised clinical trials exclude pregnant people as standard practice, very few medicines are licensed to be used during pregnancy. Autoimmune conditions often affect female patients during their potentially reproductive years. My research will focus on drugs used to treat these conditions, and particularly on drugs called monoclonal antibody biologics. I aim to understand the safety of these drugs for both the patient and fetus, and how effectively they can treat autoimmune conditions during pregnancy. First, I will use genetic variants which mimic the effects of drugs by affecting protein levels in the blood. I will test how common and rare genetic variants affect patient's outcomes in pregnancy. Second, I will look at electronic health records to compare outcomes of comparable patients with differing drug regimens during their pregnancy. Finally, I will triangulate across these different methods and summarise my findings, in order to provide further information to inform clinician's decisions.