A. A recent large study showed that the risk of MS in children of an MS patient is about 9.5% with no difference in the transmission rate for affected mothers or fathers. Another smaller study suggested a 9% rate if the affected parent is the mother and an 18% rate if the affected parent is the father. The discrepancy between the two studies has not been fully resolved. If both parents have MS the risk is further increased by 2% to 3%. In contrast, the risk of MS in siblings and non identical twins of MS patients is between 3% and 5 %. The risk is about 30% if you have an affected identical twin.
There are other factors that may affect the risk of MS in your offspring; for instance, there is evidence that pregnancy during the winter months, presumably when vitamin D levels are lower, are associated with a higher risk of MS in offspring born in the late Spring.
Since we have not identified the exact gene(s) responsible for the increased risk of MS in offspring of parents with MS, how the responsible genetic alleles from one parent interact with affected or unaffected genetic alleles of the other parent (to either increase or decrease risk) or how environmental factors modify this genetic risk, there is no way to provide further genetic counseling at this time.
It seems reasonable to at least consider planning pregnancy during the spring, summer and fall and take vitamin D during pregnancy.
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