Is pregnancy a risk factor in the causation of rheumatoid arthritis?

It is well established that the physiological changes in pregnancy can affect the course of rheumatoid arthritis (RA). Thus pregnancy is associated with remission of the disease in the last trimester, which frequently relapses after delivery.' This may be explained by the large rise in female sex hormone concentration and the subsequent fall postnatally. The disease suppression has also been related to the concentration of pregnancy serum a2 glycoprotein (PAG),2 though PAG levels in their turn are related to female sex hormones.3 The possibility that such hormones affect RA disease activity is supported by the observation that the latter fluctuates during different stages of the menstrual cycle.4 These and other studies5 have prompted increased interest as to whether female sex hormones also have a role in the causation of RA. The most prominent hypothesis is that exogenous female sex hormones, specifically the oral contraceptive pill, protect against the development of RA.