Jolting exercise may up miscarriage risk: study
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Exercise in the early stage of pregnancy, particularly high-impact exercise, may boost the risk of miscarriage, research suggests.
The reasons for this are not entirely clear, the researchers note, “but the fact that high-impact exercise seems to be associated with highest risk of miscarriage indicates that the jolts produced while exercising play a role,” they suggest.
The relatively few studies that have looked at the association between exercise in pregnancy and miscarriage have produced inconsistent results, Dr. Mette Madsen, from the National Institute of Public Health, Copenhagen, and colleagues, note in their report.
They examined information provided by 92,671 pregnant women on the time they spent exercising at different stages of pregnancy and the type of exercises they engaged in.
Roughly 47 percent of all of the women reported that they exercised during pregnancy. A total of 3,187 of the pregnancies ended in miscarriage.
The researchers found that an increasing amount of time spent on exercise each week was associated with a greater risk of miscarriage.
Exercising for up to 44 minutes per week did not raise the risk of miscarriage, but exercising for more than 419 minutes per week, between pregnancy weeks 11 to 14, raised the risk of miscarriage by nearly fourfold.
There was no association between exercise and risk of miscarriage in the later stages of pregnancy (after 18 weeks gestation).
As mentioned, the type of exercise also made a difference. Compared with no exercise, the high-impact exercise performed for 75 to 269 minutes per week raised the risk of miscarriage up to 4.7-fold, while low-impact exercise and workout/fitness-type training for the same amount of time raised the risk by about 2-fold.
A moderately elevated risk of miscarriage was seen for bicycling and horseback riding, both of which are nonweight bearing types of exercise. In contrast, swimming for 75 to 269 minutes per week was associated with a decreased risk of miscarriage compared to no exercise.
Madsen and colleagues caution that it is too early to draw any public health inferences on the basis of their findings. “Many positive effects of exercise are well established, and the findings of this study need to be replicated,” they point out in BJOG: An International Journal of Obstetrics and Gynecology.
SOURCE: BJOG: An International Journal of Obstetrics and Gynecology, November 2007.
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