Background/Purpose – The chance of miscarriage is increased after the diagnosis of rheumatoid arthritis (RA). The association of miscarriage with RA disease activity or anti-rheumatic medication is unclear, mainly due to lack of prospective studies. Our aim was to study the associations of miscarriage with RA serology, disease activity and periconceptional medication use in women with RA.

Methods – In a nationwide prospective cohort on pregnancy in RA (PARA study, 2002-2010) women with RA according to the 1987 American College of Rheumatology (ACR) criteria were visited preconceptionally, during pregnancy and after delivery or miscarriage. General characteristics and medication use were recorded and disease activity (DAS28) was measured. We analyzed the data retrospectively by logistic regression with purposeful selection of covariates, with inclusion at a significance level of p<0.20.

Results – A total of 239 preconceptional visits resulted in 181 pregnancies in 164 women. We analyzed only the first included pregnancy for each woman. Thirty (18%) of 164 pregnancies resulted in a miscarriage.

There were significant differences between women with a miscarriage and women with an ongoing pregnancy in age (33.8 (3.9) vs 32.0 (3.8) years, p=0.022) and presence of ACPA (83% vs 60%, p=0.032). The preconceptional DAS28 was higher in women who had a miscarriage (4.0 (1.0) vs 3.6 (1.2), p=0.087) and more women who miscarried had used MTX in the past (83% vs 68%, p=0.121), though these differences were not significant. There were no significant differences in RF positivity (80% vs 69%, p=0.41), and use of NSAIDs (20% vs 31%, p=0.27) or sulfasalazine (27% vs 32%, p=0.67).

Logistic regression with the occurrence of miscarriage as dependent variable, showed a tendency towards a higher OR for increasing age, presence of ACPA, increasing DAS28 or past MTX use, though none of these variables reached significance (table 1).

Twenty-one (70%) of the women who miscarried became pregnant again, of whom 19 within one year after miscarriage. This resulted in a live birth in 19 women (90%). Four women decided to stop trying to conceive. Five women were lost to follow up.

Conclusion – The miscarriage rate in the PARA study is comparable to that in the general population. However, this might be biased by a healthy cohort effect found earlier in this study. Despite having miscarried, the majority of patients were pregnant again within one year. RA patients who had a miscarriage tended to be older, to have higher disease activity, to be ACPA positive and to have a past of MTX use. This indicates that miscarriages are more likely to occur in a subgroup of RA patients with more severe disease. Although the PARA study is a large prospective cohort on pregnancy in RA, the associations found did not reach statistical significance due to the relative low frequency of miscarriages in the study.