Fertility and pregnancy

Too much exercise when pregnant may cause pre-eclampsia

zone image Effect of exercise on early stages of pregnancy

Too much physical exercise during pregnancy may result in an increased risk of pre-eclampsia, according to a recent study carried out in Scandanavia.

Preeclampsia is a condition which is found in about 1 in 14 pregnant women. It occurs after the 20th week of pregnancy and is characterised by high blood pressure and abnormal levels of protein in the mother’s urine. Although the severity of pre-eclampsia can vary, about 1 in 100 women with the condition develop the potentially life threatening eclampsia.

Previous studies have found exercise during pregnancy to be beneficial, and protect against pre-eclampsia. In this study, researchers interviewed over 85,000 women in Denmark during 1996 and 2000, and recorded the intensity and duration of physical activity when they were 12 weeks pregnant.

The scientists found that women who engaged in any intense physical activity for 270 to 419 minutes per week, had a 65% increased risk of pre-eclampsia. For women who did more than 420 minutes of intense exercise, the risk of developing pre-ecalmpsia was even higher, at 78% compared to pregnant women who did not exercise. Less than 270 minutes (four and a half hours) exercise a week did not affect the risk of pre-eclampsia.

The results took the scientists by surprise as they had expected exercise to play a more positive role. Lead researcher, Dr Sjurdur Olsen, from the Statens Serum Institut in Copenhagen, Denmark said:

"We were unable to substantiate that physical activity in early pregnancy has a protective effect against pre-eclampsia. Another unexpected finding was that leisure time exercise, in amounts that were only slightly higher than the recommended amount, seemed even to be associated with an increased risk of severe types of pre-eclampsia."

However, he also stressed that pregnant women should continue to exercise according to current guidelines, asmore research needs to be carried out.

The Royal College of Obstetricians and Gynaecologists stated:

Current RCOG advice is for women to engage in 30mins of aerobic activity each day. This works out to 210mins or three and a half hours each week.

While exercising, women should make sure that they do not get overheated as an increase in maternal temperature above 39.2 degrees Celsius may harm the fetus. A measure of the intensity of physical activity is the ‘talk test’. If women are able to maintain a conversation while exercising without feeling out of breath or uncomfortable, this is the right level of activity for them.

Professor Philip Steer, editor-in-chief of the British Journal of Obstetrics and Gynaecology where the research was published, said:

"Clinical guidelines in the UK stress that selective and moderate exercise during pregnancy can be beneficial. These include aerobic and strength-conditioning exercises. While general fitness is a good thing in many respects, these data suggest that it may be unwise to exercise to peak fitness levels."

"This new research is useful as it provides us with an indication of how much exercise pregnant women should take. As with everything in life, too much of a good thing can be bad for you, and moderation in all things remains a good policy."

This article was published on Sat 6 December 2008

Image © Karen Roach - Fotolia.com

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