Pregnancy and reproductive outcomes have been associated with altered risk of some autoimmune diseases, including rheumatoid arthritis (RA). We sought to determine whether prior pregnancy resulting in a low birth weight (LBW) infant or preterm birth is associated with a risk of subsequent RA in the mother.
We conducted an analysis of RA risk in parous women from a population-based prospective study of newly diagnosed cases of RA and age-matched healthy controls. The primary outcome measure was disease status (RA versus control), with exposures of prior preterm birth and prior delivery of an infant with LBW (≤2,500 gm), very low birth weight (VLBW; ≤1,500 gm), or extremely low birth weight (ELBW; ≤1,000 gm). A preplanned analysis including only rheumatoid factor (RF)-positive RA cases was also conducted.
A total of 202 RA cases and 1,102 controls were analyzed. Prior delivery of an infant with ELBW was associated with RA in the mother (relative risk [RR] 3.7 [95% confidence interval (95% CI) 1.0-13.2]). Prior VLBW (RR 4.0 [95% CI 1.3-11.4]) and ELBW (RR 5.5 [95% CI 1.4-22.5]) infants were associated with RF-positive RA. Prior LBW deliveries and preterm births were more common among RA cases than controls, but the differences were not statistically significant.
Compared to those with uncomplicated pregnancies, women with a prior VLBW or ELBW delivery had a higher risk of RA, particularly RF-positive RA. This association may reflect common risk factors for pregnancy complications and RA. Alternatively, complicated pregnancy itself may confer risk of subsequent RA.