Systemic lupus erythematosus (SLE) occurs predominantly in women, who represent approximately 90% of affected individuals. SLE incidence increases after puberty, peaking during the child-bearing period. Thus, endogenous and exogenous sex hormones are thought to play an important role in SLE etiology. Notably, estrogen in oral contraceptives (OCs) has been questioned, since estrogen can influence the immune system and may promote autoimmunity . Some studies have reported alterations in SLE disease activity during pregnancy, with OC use, and even with menstrual cycles, further s uggesting a role for estrogen [2–4]. Until recently, the etiologic role of OCs was debated because observational studies, hampered by methodological limitations, had produced conflicting results (Table 1) [5–10]. This year, a large nested case–control study was reported, which brought new evidence to the debate .