Researchers in Sweden identified 77 patients with rheumatoid arthritis and 308 matched controls. Using birth records, they collected information such as birth weight, mother's age, length of hospital stay after delivery, start of breast feeding during the hospital stay, and father's occupation (manual or non-manual worker).
They found that high birth weight (4000g or more) was positively associated with rheumatoid arthritis but low birth weight was not. Initiation of breast feeding during the hospital stay and the father's occupation were also associated with rheumatoid arthritis. They found no other significant associations.
"Our findings indicate that characteristics of the perinatal period may be of aetiological importance in the pathogenesis of rheumatoid arthritis," they conclude.