Both organ-specific and systemic autoimmunity are associated with an increased prevalence of recurrent miscarriage (RM). The precise mechanism for this is unclear, as cross-reactivity between trophoblastic and maternal host autoantigens has not been demonstrated. In the antiphospholipid antibody syndrome, prothrombotic mechanisms are evident, along with direct inhibitory actions against trophoblastic activity. In many types of both systemic and organ-specific immunity, however, a disturbed T-helper cell profile is seen. This is also evident in women with RM. In both cases, reduced numbers of T regulatory cells have been reported. These are required to regulate excessive activity of the Th1 and the proinflammatory Th17 subsets that, when operating through excessive natural killer cell activity, may have antipregnancy effects. Checking for underlying autoimmunity is therefore a critical analysis in women with RM and future therapies will probably be aimed at correcting the deficiency of regulatory T cells or correcting excessive Th1 and Th17 function.