Rheumatoid arthritis during pregnancy and postnatal catch-up growth in the offspring.

Objective: Active rheumatoid arthritis (RA) during pregnancy and the presence of rheumatoid factor (RF) or anti-citrullinated protein antibodies (ACPAs) are associated with lower birth weight of the child. Moreover, treatment of the mothers with prednisone may shorten the gestational age at birth. Rapid catch-up in weight for length during the first year of life has been related to a worse cardiovascular and metabolic profile in early adulthood. This study was therefore undertaken to assess the influence of RA disease activity, medication use, and presence of RF or ACPAs during pregnancy on the growth of the child in the first year of life.

Methods: Among 180 children born to mothers with RA, the tempo of catch-up in weight during the first year of life was studied. Independent variables were the extent of RA disease activity (according to the Disease Activity Score in 28 joints [DAS28]), medication use, and presence of RF or ACPAs during pregnancy.

Results: Of 167 children with available data, 52 (31%) showed catch-up in weight in the first year of life, of whom 90% (47 of 52) showed rapid catch-up. An elevated DAS28 score in the mother was associated with rapid catch-up in weight of the offspring, independent of maternal medication use or the presence of RF or ACPAs during pregnancy (odds ratio 1.44 [95% confidence interval 1.07-1.95] per 1-point increase in the DAS28). Use of medications during pregnancy had no influence on postnatal growth.

Conclusion: Elevated RA disease activity during pregnancy should be avoided because it is associated with rapid postnatal catch-up in weight, a risk factor for a worse cardiovascular and metabolic profile in adults. Medication for RA during pregnancy, including prednisone, had no effect on growth. Continuation or extension of medication will not only improve maternal health during pregnancy, but could be beneficial for the future health of the unborn child.