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Postpartum onset of rheumatoid arthritis and other chronic arthritides: results from a patient register linked to a medical birth registry
  1. M Wallenius1,2,
  2. J F Skomsvoll1,2,
  3. L M Irgens3,
  4. K Å Salvesen4,5,
  5. W Koldingsnes6,
  6. K Mikkelsen7,
  7. C Kaufmann8,
  8. T K Kvien9
  1. 1
    Department of Rheumatology, Trondheim University Hospital, Trondheim, Norway
  2. 2
    Department of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway
  3. 3
    Medical Birth Registry of Norway, Locus of Registry Based Epidemiology, Institute of Community Medicine and Primary Health Care, University of Bergen and Norwegian Institute of Public Health, Bergen, Norway
  4. 4
    National Centre for Fetal Medicine, Trondheim University Hospital, Trondheim, Norway
  5. 5
    Department of Laboratory Medicine, Women’s and Child Health, Norwegian University of Science and Technology, Trondheim, Norway
  6. 6
    Department of Rheumatology, University Hospital, Northern Norway, Tromsø, Norway
  7. 7
    Department of Rheumatology, Lillehammer Hospital for Rheumatic Diseases, Lillehammer, Norway
  8. 8
    Department of Rheumatology, Buskerud Central Hospital, Drammen, Norway
  9. 9
    Department of Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  1. Correspondence to Dr M Wallenius, Department of Rheumatology, St Olav’s Hospital, Bevegelsessenteret, N-7006 Trondheim, Norway; marianne.wallenius{at}


Background: It is known that onset of rheumatoid arthritis (RA) is increased post partum.

Objective: To compare incidence rates between RA and other chronic arthritides (OCA) 0–24 months after delivery, and to compare the incidence rates within each group 0–24 versus 25–48 months post partum.

Methods: Premenopausal women from a Norwegian patient register were linked with the Medical Birth Registry of Norway to study the interval between delivery and time of diagnosis. Cox regression analysis with adjustments for age at delivery and birth order was applied to compare proportions of incident cases of RA and OCA with onset 0–24 months post partum. Poisson regression analysis with adjustment for the population at risk was applied to estimate the incidence rate ratio (IRR) 0–24 versus 25–48 months post partum.

Results: Of 183 RA and 110 patients with OCA diagnosed after delivery, 69 (37.7%) had RA and 31 (28.2%) OCA during the first 24 months post partum (p = 0.09). The IRR (95% CI) for diagnosis during 0–24 months versus 25–48 months was 1.73 (1.11 to 2.70) (p = 0.01) for RA, 1.05 (0.59 to 1.84) (p = 0.86) for OCA. The IRR was 2.23 (1.06 to 4.70) and 1.87 (0.67 to 5.21), respectively, when only considering diagnoses after the first pregnancy. Clinical characteristics were similar within each diagnostic group.

Conclusion: The proportions of incident cases with onset 0–24 months after delivery were not different between RA and OCA. A peak in incidence during 0–24 months was seen in the RA group, both when considering all pregnancies and only the first pregnancy.

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  • Funding Research grants for the NOR-DMARD register have been received from Abbott, Amgen, Aventis, BMS, MSD, Roche, Schering-Plough/Centocor, Wyeth and the Norwegian Directorate for Health and Social Affairs. This actual work was supported by the liaison committee between the Central Norway Regional Health Authority (RHA) and the Norwegian University of Science and Technology (NTNU).

  • Competing interests Hans Bijlsma was the Handling Editor for this article.

  • Ethics approval Approval from the regional ethic committee of Central Norway.

  • Provenance and Peer review Not commissioned; externally peer reviewed.

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