Grand Challenges in MS (8): how does pregnancy affect MS?

#MSBlog: Grand Challenge (8): What are the mechanisms that underlie the observed reduction in relapse rates in the last third of pregnancy? 

“As you are aware pregnancy affects the natural history of MS; what are the mechanisms that underlie these effects? If we can define them we may be able to mimic a state of pregnancy, i.e. pseudopregnancy, and use this to treat MS.”

How does MS affect the natural history of MS?

1. There is a reduced risk of developing MS in woman who have had children compared to woman without children. The risk associated between not having children and MS increases with age. In addition, there is a significantly decreased risk of a progressive course in women who became pregnant after MS onset.

Runmarker and Andersen. Pregnancy is associated with a lower risk of onset and a better prognosis in multiple sclerosis. Brain. 1995 Feb;118 ( Pt 1):253-61.

2. When you look at the relapse rate in each 3 month period, or trimester, during pregnancy and compare it with the rate during the year before the pregnancy, there is a clear drop during the third trimester. In one large study the average rate of relapse was 0.7 per year in the year before pregnancy, 0.5 during the first trimester, 0.6 during the second trimester and 0.2 during the third. The down side is that the rate increased to 1.2 during the first three months after pregnancy and then returned to the pre-pregnancy rate. 

“Could these observations be due to the hormonal effects of pregnancy? There are numerous studies documenting extensive immunological changes during pregnancy. The subject is very broad and complex and needs further exploration. This review article helps define the issues.”

Mor & Cardenas. The immune system in pregnancy: a unique complexity.Am J Reprod Immunol. 2010 Jun;63(6):425-33.

….. Our challenge as scientists and clinicians interested in the field of reproductive immunology is to evaluate many of the ‘classical concepts’ to define new approaches for a better understanding of the immunology of pregnancy that will benefit mothers and fetuses in different clinical scenarios.

Should we be using pregnancy as a treatment for MS? 

“Of course not, but this information is potentially useful to woman with MS her may be planning to have children.”
“The issue of whether or not MSers should have children has been debated extensively on this blog and is beyond the brief of this post. My position remains the same; is it is up to the MSer and their partners to decide on this issue.”

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