Perinatal factors and adult-onset lupus.

Objective: Some evidence suggests that perinatal factors, including birth weight and breastfeeding, may influence the occurrence of autoimmune rheumatic diseases. However, few studies have investigated these factors in patients with systemic lupus erythematosus (SLE). Therefore, we evaluated the role of birth weight, being breastfed, and preterm birth on the incidence of SLE in participants in the Nurses' Health Study (NHS) and the Nurses' Health Study II (NHSII).
Methods: We studied 87,411 NHS participants and 98,413 NHSII participants without SLE at baseline who provided information on perinatal exposures. Among these women, during 26 (NHS) and 14 (NHSII) years of followup, 222 incident SLE cases were confirmed (136 NHS and 86 NHSII) by medical record review using American College of Rheumatology criteria. We used stratified Cox models to estimate the association of perinatal factors with SLE, adjusting for race, early passive cigarette smoke exposure, and parents' occupation. A random-effects meta-analysis was used to compute combined estimates across the 2 cohorts.
Results: After adjustment for multiple potential confounders, high birth weight (> or =10 pounds) was associated with increased rates of SLE compared with normal birth weight (7-8.5 pounds; rate ratio [RR] 2.7, 95% confidence interval [95% CI] 1.2-5.9), as was being born > or =2 weeks preterm (RR 1.9, 95% CI 1.2-3.0); however, being breastfed was not (RR 0.8, 95% CI 0.6-1.1).
Conclusion: Birth weight > or =10 pounds and preterm birth were both positively associated with incident SLE among women.