The biologic era and pregnancy in rheumatoid arthritis: a prospective multicenter study from the Norwegian RevNatus...

It is known that pregnancy affects disease activity in Rheumatoid arthritis (RA), but earlier studies have shown conflicting results regarding the degree of change and the role of antibodies. Few studies have been conducted on patients with use of Tumor Necrosis Factor-α Inhibitors (TNFi) throughout pregnancy. The aims of this study were to investigate disease activity in women with RA from preconception to 12 months postpartum and assess the influence of anti-cyclic citrullinated protein antibodies (ACPA), rheumatoid factor (RF), erosive disease, and time trends.

This prospective multicenter cohort study used data from the Norwegian RevNatus registry (2007-2024). Women with RA were followed before pregnancy, each trimester, and until 12 months postpartum. We assessed disease activity using Disease Activity Score in 28 joints with C-Reactive Protein (DAS28(3)CRP). Linear mixed models were used to evaluate changes over time and interactions with ACPA, RF and erosions, and we divided pregnancies into three groups by year of delivery. Flares were defined as a change of DAS28(3)CRP > 1.2.

A total of 598 pregnancies in 475 women were included. The estimated mean DAS28(3)CRP decreased from 2.39 in 2^nd to 2.27 in 3^rd trimester (p = 0.003) and increased significantly to 2.52 (p < 0.001) at 6 weeks postpartum with 16% experiencing flares. The proportion improving during pregnancy was 11%, but 49% in those with DAS28(3)CRP > 3.2 in 1^st trimester. Seropositive women had more fluctuations during pregnancy and higher postpartum activity; seronegative women showed minimal variation. Erosive disease did not have a significant effect. Disease activity before, during and after pregnancy decreased in later years of delivery, corresponding to increased use of TNFi.

Most women with RA maintained remission during pregnancy, but postpartum flares still occurred. Improvement was seen in pregnancies with initial high disease activity, but not in women with well managed disease. Seropositive women experienced higher disease activity and larger increase in DAS28(3)CRP postpartum. Women with pregnancies after 2020 had consistently lower disease activity compared to those who were pregnant in 2007-2019, coinciding with broader TNFi use during pregnancy.