Over exercising early in pregnancy could increase the risk of miscarriage threefold.
Danish Researchers found jogging, ball games and racket sports all increased the risk - as did more than seven hours of exercise a week. Government advice is, however, to continue exercise, where possible, throughout pregnancy.
The study was carried out at the University of Southern Denmark, who questioned more than 90,000 women on their exercise regime, then linked the answers to the outcome of their pregnancies. Compared with those who did no exercise at all, women who played "high-impact" sports or who exercised for more than seven hours a week were approximately three-and-a-half times more likely to miscarry. Miscarriage is much less common later in pregnancy, and after the 18-week mark, the link between exercise and miscarriage disappeared.
The study was originally published in the British Journal of Obstetrics and Gynaecology, and the authors wrote: "The results of this study suggest that leisure time exercise during pregnancy, and particularly high-impact exercise, is associated with an increased risk of miscarriage in the early stage of pregnancy." But they admitted that the format of the research - asking women to recall what exercise they did during pregnancy - was imperfect. It also did not take into consideration the fact that women who later miscarry are far less likely to experience morning sickness, which might be a reason they were able to exercise early in pregnancy.
It was noted that some forms of exercise did not appear to increase the risk - including swimming, one of the most popular among pregnant women. The government's official advice is for women to keep up their normal daily physical exercise routine for as long as they feel comfortable. It suggests that women who were inactive before pregnancy shouldn't embark on a new strenuous fitness regime, but should aim for a little moderate exercise every day.
It's not recommended to participate in sports which involve the risk of an impact to the abdomen of a pregnant woman but lighter exercise like jogging shouldn't cause problems. The benefits of exercising during pregnancy are obvious as it improves the cardiovascular system, and maintains muscle tone.