There's a new Australian study being picked up by the media on pregnancy and MS.
A study by the Murdoch Childrens Research Institute in Victoria, published today, found women with at least one child have about half the risk of early MS symptoms compared to women without children. The risk of developing symptoms of the incurable disease appear to drop with each additional child. For example, women with three children have a 75% lower risk of early MS symptoms compared to women without children.
Lead researcher Anne-Louise Ponsonby says although the study found only an association between pregnancy and a lower risk of MS symptoms - not a direct cause-and-effect link - it could help explain why the incidence of MS in women has increased in past few decades.
"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," Ms Ponsonby said in a statement. The study, which involved 800 women, also found the benefits of pregnancy seemed to remain even after researchers accounted for other factors such as smoking, skin damage and sun exposure and certain susceptibility genes. "In our study, the risk went down with each pregnancy and the benefit was permanent."
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Naturally, there is lot of discussion on how the immune system is modulated while carrying a fetus...something the body sees as "other" and how this might affect MS. And many people have mentioned hormones, especially estrogen.
But I wanted to discuss the vascular changes that happen while a woman is pregnant, because I never see this discussed, and I hope to encourage the ISNVD and other MS researchers to look into this correlation.
During pregnancy, a woman's blood volume increases by 50%. This is to nourish the placenta and growing fetus, and also to compensate for blood loss during delivery. If the blood vessels remained the same, with more blood volume, blood pressure would become dangerously high....so, the veins become more pliant, open and relaxed. This is why many women develop varicose veins or hemorrhoids during preganancy.
Venous Distension increases approximately to 150% during the course of gestation and the venous ends of capillaries become dilated. Hormonal factors cause the veins to become more compliant. Together with the increased venous pressure that occurs later in pregnancy, these factors cause significant venous distension. Venous distendibility follows the rise in the hormones progesterone and relaxin. Relaxin works by softening collagen and elastin in the tissues. It loosens the strong, cord-like fibers until they are super-pliable.
The hormone Relaxin is now being studied in cardiovascular disease, for its affects on the endothelium, via nitric oxide mechanisms.
The ovarian peptide hormone, relaxin, circulates during pregnancy, contributing to profound maternal vasodilation through endothelial and nitric oxide (NO)–dependent mechanisms. To conclude, relaxin is a novel regulator of BMDECs number and function, which has implications for angiogenesis and vascular remodeling in pregnancy, as well as therapeutic potential in vascular disease.
http://bloodjournal.hematologylibrary.org/content/119/2/629.abstract
Cerebral bloodflow increases during pregnancy:
Internal carotid artery blood flow volume increased during pregnancy from 318 mL/min ± 40.6 mL/min in the first trimester to 382.1 mL/min ± 50.0 mL/min during the third trimester, corresponding to CBF values of 44.4 and 51.8 mL/min(-1)/100 g(-1), respectively (P < .0001). CBF changes were associated with progressive decrease in cerebral vascular resistance and moderate increase in ICA diameter.
CONCLUSION:
Maternal CBF is gradually increasing during normal pregnancy. Vasorelaxing impact of estrogens and other factors on cerebral vessels may explain the changes in CBF during pregnancy.
http://www.ncbi.nlm.nih.gov/pubmed/20599183
Could the hormonal relaxation of the jugular and azygos veins and increased blood volume during pregnancy account for better cerebral/spinal bloodflow? Could this be why MS symptoms are less during pregnancy, why pregnancy appears to "protect" women from MS?
more questions to ask, and to be answered--
Joan
