The AusImmune study, funded by the US National MS Society, Australia’s National Health and Medical Research Council and MS Research Australia, studied a large group of Australians presenting with their first episode of MS-like symptoms with the aim of understanding the environmental risk factors for MS.
The study recorded information on factors such as viral infections, vitamin D levels, sun exposure and smoking in over 800 people including 300 who had experienced MS symptoms. For women, the number of pregnancies lasting at least 20 weeks and the number of live births were also recorded.
Prof Anne-Louise Ponsonby of the Murdoch Children’s Research Institute in Melbourne who led the study, and her colleagues, found women with at least one child had about half the risk of developing early MS symptoms. Women with three children had a 75 per cent lower risk of early MS symptoms.
These important results from the AusImmune study were published in Neurology on 7 March 2012.
The number of children born was also analysed for men, but did not relate to the risk of men developing MS.
Prof Ponsonby, said the effects of pregnancies remained even after they had taken into account other factors such as smoking, skin damage and sun exposure, and certain susceptibility genes.
“The rate of MS has been increasing particularly among women over the last few decades, and our research suggests that this may be due to mothers having children later in life and having fewer children than they’ve had in past years,” she said.
The mechanism of how pregnancy protects against the development of MS remains unknown, however, pregnancy is known to modulate the immune system and induce a state of tolerance to the foetus and placenta.
It is also known that women with MS can experience a reduction in MS relapses during pregnancy, however, there is an increased risk of a relapse in the three months after the baby is born. Pregnancy does not affect the long-term progression of MS or level of disability.
Understanding the details of how pregnancy affects MS risk and MS disease activity will provide vital clues to the mechanisms of MS and potential treatments. There is a considerable international research effort to understand the effects of pregnancy on MS.
In particular MS Research Australia has funded a research project into the effects of pregnancy in a laboratory model of MS. Read more here
Further information on pregnancy and MS from MS Australia is available here