Introduction: To collect nationwide data in Iceland on pregnancy and its outcomes among female patients with active inflammatory arthritides we linked two registers, the ICEBIO register and the Icelandic Medical Birth Register.

Methods:
We used multivariate analysis to evaluate the risk of preterm birth, Caesarean section, low Apgar score at 5-minutes and low birth weight among females with inflammatory arthritis (rheumatoid arthritis (RA), psoriatic arthritis (PsA) and ankylosing spondylitis (AS)) in comparison with healthy controls matched on age and parity. We also investigated pregnancies before and after the diagnosis of respective rheumatic disease and especially in respect to treatment with TNFα inhibitors (TNFi).

Results: In the end of 2016, 723 female patients were registered in ICEBIO as they had received treatment with TNFi due to inflammatory arthritis. Of those, 412 women had given birth to 801 children, whereof 597 were delivered before confirmed diagnosis of the mother and 53 were delivered after the start of the TNFi treatment. Relative risk of Caesarean section among these female with various arthritis conditions were 1.47 (95% CI: 1.19-1.82; p < 0,001) compared to controls and was highest in the group with PsA or 2.06 (1.41-3.02; p<0,001). We did not find increased risk of preterm delivery or low Apgar score. Patients with inflammatory arthritis had lower risk of children with low birth weight or 0.37 compared to healthy controls (95% CI: 0.36-0.37; p < 0.05). Due to low numbers of deliveries after the initiation of TNFi therapy (n=53) we were not able to perform any analysis for that group.

Conclusion: Icelandic female patients with inflammatory arthritis are at an increased risk of Caesarean section in comparison to healthy controls. However, their newborns are in good condition and healthy at birth. Analysis of the impact of treatment with TNFi on pregnancy is not yet possible due to limited data.