During pregnancy, many important biological and physiological changes occur to protect both mother and the growing baby, particularly related to hormones and the immune system. We also know that compared to men, women are more likely to have autoimmune disorders, where the body's defence system attacks itself. However, pregnant women are often excluded from studies because of safety implications. We now need to figure out how reproductive hormones might impact autoimmune disorders in both pregnant and non-pregnant people, as well as what other health behaviours may influence this.