The role of pregnancy in the course and aetiology of rheumatoid arthritis.

The aetiology of rheumatoid arthritis (RA) is unknown, although being female is generally recognized as the most important independent risk factor, the disease being 2 to 3 times more frequent in females than in males. The dramatic effect of pregnancy in rheumatoid arthritis has been documented for over 50 years. This review examines the evidence and possible mechanisms by which pregnancy modifies the disease process and may alter predisposition to the development of RA in later life.