The onset of rheumatoid arthritis in relation to pregnancy and childbirth.

It has been suggested that the onset of RA symptoms is reduced during pregnancy and increased in the postpartum period. In the present study symptom onset in relation to the pregnancy prior to disease onset was compared between 135 young RA patients with definite RA and 378 controls with soft tissue rheumatism or osteoarthritis. Two RA patients developed symptoms during pregnancy versus 9 controls (odds ratio OR = 0.64). In the 3 months postpartum 5 RA patients and 5 controls developed symptoms (OR = 3.37). These results show the same trend as those of previous studies, i.e. a decrease in the onset of RA during pregnancy and an increased onset of RA after delivery. These findings might be explained by a delayed clinical onset of RA that started during pregnancy, analogous with the ameliorating effect of pregnancy on the course of existing RA and the flare-up of disease activity in the postpartum period.