Women’s risk for developing clinically isolated syndrome, which often leads to multiple sclerosis, was shown to decrease with increased number of pregnancies in a comprehensive study undertaken in Australia. Clinically isolated syndrome (CIS) is a first neurologic episode caused by inflammation or damage to nerve fiber-insulating myelin in the brain or spinal cord. Although the results of this Ausimmune Study need to be confirmed, the findings encourage further exploration of potential treatments such as sex hormones, which may mimic pregnancy’s benefits in women with MS. The sex hormone estriol is currently in clinical trials, supported by the National MS Society and the National Institutes of Health, to treat women MS.
Anne-Louise Ponsonby, PhD (Murdoch Childrens Research Institute, Melbourne) and colleagues across Australia report their findings in Neurology (2011;76:540-548). This study was supported by a research grant from the National MS Society to Anthony McMichael, PhD, the National Health and Medical Research Council of Australia, and MS Research Australia.
Background: Before 1950, most women with MS were counseled to avoid pregnancy because of the belief that it might make their MS worse. Over the past 40 years, studies in hundreds of women with MS have almost all reached the opposite conclusion: that pregnancy reduces the number of MS exacerbations, especially in the second and third trimesters.
The Ausimmune Study was undertaken to investigate whether increased exposure to sunlight and vitamin D may be protective against MS in people who had not yet been diagnosed with MS, but who had experienced a CIS. Read more about previously released findings. In the current study, the team used this unique population to study whether the number of pregnancies or offspring affects the risk for developing a CIS.
The Study: Investigators looked at the records of 282 men and women who had developed a CIS, and compared the number of children – and in women, the number of pregnancies – with controls who did not develop CIS.
Women who had one pregnancy were nearly half as likely to develop CIS, and those with three or more pregnancies had more than one fourth the risk of developing CIS compared with controls. Other factors considered – such as sun exposure and immune-system-related genes associated with MS – did not otherwise explain these associations. There was no association between risk of CIS and the number of children in men.
Comment: In an accompanying editorial, Martin Daumer, PhD, Brian G. Weinshenker, MD, and Rhonda Voskuhl, MD, comment that these findings need to be replicated in other countries to be validated, and caution that the study does not address whether pregnancy affects the long-term course of MS or development of disability.
Even with these caveats, the editorial authors say that because of studies such as this one, there is a compelling need for research to develop therapeutic approaches that mimic pregnancy’s benefits in women with MS. Dr. Voskuhl is now leading a team of investigators at seven medical centers to conduct a two-year, controlled clinical trial of estriol – a sex hormone that is increased during pregnancy – added to standard therapy to treat MS in 150 women with relapsing-remitting MS. This study recently completed enrollment.
This study provides additional evidence of a link between gender and autoimmunity. Read more about the Society’s efforts to study this link for clues to stopping MS in its tracks and ending it forever.