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Gender, Sex, Childbirth and Multiple Sclerosis


So is getting MS just a question of where you're born?

Of course not. It's at least as much who you are as it is where you're brought up. It's your genetic make up interacting with some unknown environmental factors only one of which is where you are raised. Who you are is inevitably a product of who your parents are and who their parents are. In this section I intend to go through some of the non-geographical risk factors involved in developing MS and associated with MS relapses. As with the last section, most of this information is based on statistical data, a topic I will go into later.

So what are these risk factors?

Perhaps the most obvious risk factor is female sex. Results from data on the correlation between gender and MS varies significantly from country to country and from survey to survey. This strikes me as rather odd, since sex is a rather obvious variant and there is no shortage of PwMS to perform such a simple analysis. In all studies, MS affects women more than men, but the female to male ratio varies from 2.79:1 down to 1.65:1. It is possible that this is explainable by statistical clustering but there could be something else at play here. Many people in the UK, some neurologists and the MS Society of Great Britain included, believe that the female to male ratio in the UK is 1.5:1, but I have found no evidence to support this belief on MedLine and only a lot studies confirming the 2:1 ratio reported from other countries.

The sub-group of PwMS with the Primary Progressive form of the disease do exhibit a different gender ratio to those with other forms of the disease. Again statistics for these ratios are subject to the usual vagaries, but, in general, it seems that men are at much at risk of getting PPMS as women.

Why do women get MS more than men?

This is yet another question that is difficult to answer without knowing what causes MS in either sex. There is compelling evidence that there is, at least, some autoimmune component to the disease. Most autoimmune diseases affect women more than men and often the female to male ratio is much greater than it is in MS. The different and more variable nature of the biochemistry of women's bodies is likely to play a role especially since the naturally occurring sexual hormones oestrogen, progesterone and testosterone all have an immuno-modulating function.

It is also the case that women's genetic make-up is different to men's, having two X-chromosomes whereas men have one X- and one Y-chromosome. Whether one or more of the hypothetical multi-factorial genes that confer an increased risk of MS or other autoimmune diseases lies on the X-chromosome is something worth considering.

So if female hormones affect the risk of developing MS, does pregnancy affect MS?

Indeed it does. Several studies have examined the influence of pregnancy on multiple sclerosis and their results do not, in the main, countenance against women with MS getting pregnant. Surveys of relapse rates as well as MRI scans confirm that pregnancy, itself, significantly reduces the chances of having a relapse. Furthermore, synthetic estradiol (a commonly prescribed form of oestrogen) drug trials in women has also been shown to reduce relapse rates. This is very promising for women, but obviously rather less so for men.

So does pregnancy slow down the course of the disease?

Well, yes and no. During pregnancy relapse rates are reduced but in the three months after birth it rises significantly before falling back to the pre-pregnancy levels. So, although pregnancy and childbirth cause changes in relapse rate, they have no long term effect on the overall course of the disease. [Confavreux et al, 1998]

Reseach into other associated factors such as breastfeeding [Nelson et al, 1988] and epidural pain treatments [Confavreux et al, 1998] show them to have no effect on the course of MS. Nor does the mother having MS seem to have any negative consequences for the health of the child beyond an increased risk of developing the disease.

Of course, bringing up children is demanding and tiring work and MS itself can cause chronic fatigue as well as other disabilities which may make the nature of parenthood slightly different to that of people without MS. Couples where one or both members have MS need to consider such factors and it may well be that a partner without MS has to take on more responsibilities than would otherwise be expected. However, many PwMS successfully have families and there is no evidence that the children are in anyway damaged by having a parent with MS.

Some neurologists and other health care professionals have, in the past, advised women against getting pregnant, but various surveys show this caution to be unfounded.

But what are the risks that my children will will develop MS?

People who have relatives with multiple sclerosis are more likely to develop the disease than people with no family history of MS. It seems clear from various population studies that there is a genetic susceptibilty involved in contracting the disease.

This does not mean, however, that MS is a genetic disease in the way that cystic fibrosis or sickle cell aenemia are genetic diseases. Let me try and explain why.

Humans, in common with other sexually reproducing animals, have two copies of most genes. For example, we all have two copies of the gene responsible for eye colour. Similarly, we all have two copies of a gene responsible for normal functioning of the mucus glands. However, in cystic fibrosis, a genetic disease, there has been a mutation to this gene. People who have just one copy of this abnormal gene will be perfectly healthy but people with two copies of this gene will always get cystic fibrosis.

This is a 100% certain - there are no cases of people with two copies of the cystic fibrosis mutation who do not have the disease.

Multiple Sclerosis, in common with most other autoimmune conditions, is not like this. Despite the fact that there appears an inherited risk of contracting MS, it is clear that even people with a genetic predisposition to contract MS only have a one chance in three of getting the disease. We know this from studies of identical twins in which one twin has MS. It turns out that the other twin only gets MS in 66%

Having a child is a beautiful and rewarding experience and it is my belief that

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