ObjectivesReports on pregnancy outcomes among women with juvenile onset arthritis (JIA) have been few and small. The aim of this study was to assess pregnancy outcomes in a large and contemporary cohort of women diagnosed with JIA.MethodsIn a nationwide Swedish population-based cohort study between 1992 and 2011, we identified 1807 births among women with JIA and 1 949 202 control births. Since JIA is a heterogenic condition, births to women with JIA was divided into JIA paediatric only (n=1169) and JIA persisting into adulthood (n=638). ORs and 95% CIs were estimated with generalised estimating equations.ResultsWomen with JIA were at increased risk of preterm birth, especially medically indicated, in both subgroups: adjusted OR (aOR) 1.74 (1.35–2.67) for JIA paediatric and aOR 4.12 (2.76–6.15) for JIA persisting into adulthood. JIA persisting into adulthood was associated with very preterm birth (aOR 3.14, 1.58–6.24), spontaneous preterm birth (aOR 1.63, 1.11–2.39), small for gestational age birth (aOR 1.84, 1.19–2.85), early-onset pre-eclampsia (aOR 6.28, 2.68–13.81) and late-onset pre-eclampsia (aOR 1.96, 1.31–2.91). Women with JIA paediatric only were at increased risk of delivery by caesarean section (aOR 1.42, 1.66–1.73) and induction of labour (aOR 1.45, 1.18–1.77).ConclusionsWe found increased risks of both maternal and infant complications among women with JIA confined to childhood and in women with JIA persistent into adulthood as compared with population controls. Pregnancies in women with JIA should thus be subject to increased surveillance during pregnancy and delivery.