Influence of HLA-class II incompatibility between mother and fetus on the development and course of rheumatoid arthritis of the mother.

OBJECTIVE To assess the relation between the course of rheumatoid arthritis (RA) during pregnancy or the onset of RA postpartum and DRB1, DQA1, and DQB1 incompatibilities between mother and child. METHODS In 45 pregnancies of 33 RA patients the course of RA was related to the number of class II incompatibilities. Furthermore class II incompatibilities in 16 pregnancies followed by RA onset were compared with those in 87 control pregnancies. RESULTS The risk of a favourable compared with an unfavourable course was 0.95, 2.67, and 2.38 in case of DRB1, DQA1, and DQB1 incompatibility respectively. DQA1 and DQB1 incompatibilities were seen more often in the 10 pregnancies followed by RA onset within three months than in control pregnancies (OR 8.02, 95% CI 0.97, 66.06 and OR 8.79 95% CI 1.07, 72.46 respectively). CONCLUSIONS DQA1 and DQB1 incompatibility between mother and child seems to have a favourable effect on the course of RA and may postpone the risk of RA onset during pregnancy.