WESTPORT, CT (Reuters Health) Oct 2 - Neither pregnancy nor the use of oral contraceptives affects the risk of contracting multiple sclerosis, according to Dr. Miguel A. Hernan and associates.
"There were a lot of experimental data in animals indicating that there might be an association," Dr. Hernan, of the Harvard School of Public Health, in Boston, told Reuters Health.
Dr. Hernan's group evaluated data from the Nurses' Health Study and the Nurses' Health Study II in the US. They excluded patients who had a diagnosis of MS before the baseline questionnaires were administered in 1976 and 1989, respectively. From over 200,000 subjects, the investigators documented 315 definite or probable cases of MS that developed after the baseline assessments. Their findings appear in the September 26th issue of Neurology.
After the researchers adjusted for age, smoking, latitude and ancestry, the relative rate of MS diagnosis for those who had ever used oral contraceptives was 1.1 when compared with never users. The investigators saw no clear trend in MS risk with increasing duration of use. "Neither parity nor age at first birth were associated with the risk of MS," Dr. Hernan and his colleagues write.
"Our study is the largest one to study these issues," Dr. Hernan said, "so we are now in much better position to say that there doesn't seem to be any association between being on oral contraceptives and the risk of MS."
"That doesn't mean that women with MS may not benefit from being on estrogens," he added. "That is a separate question that we cannot answer here."