London, Dec 3 : Women who take more than four and half hours of exercise a week during pregnancy are at an increased risk of suffering from dangerously high blood pressure, a study has shown.
The results of the study, which involved more than 85,000 pregnant women, are astonishingly as it is widely believed that exercise have a beneficial effect on pregnant women.
Currently, pregnant women are recommended to take 30 minutes of moderate intensity exercise per day - and the latest data suggest that exceeding that by even a small amount was linked to pre-eclampsia.
To reach the conclusion, Danish and Norwegian researchers looked at medical data of thousands of women in Denmark who were pregnant between 1996 and 2002.
The study found that jogging for more than one hour and 15 minutes a week more than doubled the risk of pre-eclampsia.
Women with high levels of physical activity, 4.5 hours a week to seven hours a week, were 65 per cent more likely to have severe pre-eclampsia, the research found, reports the Telegraph.
Women who did more than seven hours a week of exercise were 78 per cent more likely to have the condition, meaning 29 per cent of women who do this much exercise will develop severe pre-eclampsia.
Senior author, Dr Sjurdur Olsen, from the Statens Serum Institut in Copenhagen, Denmark and Adjunct Professor of Nutrition at the Harvard School of Public Health in Boston, USA said: "Recommendations have been issued in several countries that pregnant women should exercise at least 30 minutes each day. An important underlying contention is that this can reduce risk of pre-eclampsia. In our study, 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.
"Further research is needed in other large prospective cohort databases which are now emerging in several countries. Until that has happened, recommendations in the field should remain unchanged." The study has been published in the British Journal of Obstetrics and Gynaecology.