Children Born by Women With Rheumatoid Arthritis and Increased Susceptibility for Chronic Diseases: A Nationwide Cohort Study. 
Fetal exposure to maternal rheumatoid arthritis (RA) might impact the long-term risk of disease in the offspring.  We examined a possible association between maternal RA and 15 selected groups of chronic diseases in the offspring.  This nationwide cohort study was based on the Danish health registries and included data on all children born alive in Denmark between January 1, 1989 and December 31, 2013.  The cohort comprised 2,106 children born by women with RA (exposed), and 1,378,539 children born by women without RA (unexposed).  Cox proportional hazards regression models were used, taking a large range of confounders into consideration, and the hazard ratios (HRs) of child and adolescent diseases were calculated.  In children exposed to maternal RA in utero, the HR of thyroid diseases was 2.19 (95% confidence interval [95% CI] 1.14-4.21), epilepsy 1.61 (95% CI 1.16-2.25), and RA 2.89 (95% CI 2.06-4.05).  The HRs for anxiety and personality disorders and chronic lung disease including asthma were in the range of 1.15-1.16, but these were not statistically significant associations.  Our results suggest that in utero exposure to maternal RA is associated with an increased risk of thyroid disease and epilepsy in childhood and adolescence, and in particular an increased risk of RA, compared to children born to mothers without RA.  These important findings should encourage pediatricians and general practitioners to have an increased awareness of certain chronic diseases in children exposed to RA in utero.