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Does Exercise Cause Miscarriages and Pregnancy Loss?

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Updated October 09, 2007

Question: Does Exercise Cause Miscarriages and Pregnancy Loss?
Answer:

Miscarriages are usually no one’s fault, and conventional advice has usually been that exercise does not cause miscarriages. In fact, doctors often encourage pregnant women to exercise, given that exercise can help women to stay in shape and keep weight gain within desired limits.

However, a study published in BJOG in October 2007 concluded that strenuous exercise before the 18th week of pregnancy may increase the risk of miscarriages. The researchers found an increasing correlation between the number of hours per week that a woman exercised and the likelihood of miscarriage, as well as an association between high impact exercise and miscarriage.

Previous studies have found no link, but the Danish study surveyed 92,671 women in the Danish National Birth Cohort and interviewed the women about their exercise habits to establish a hazard ratio. The researchers did urge caution in interpreting the results, given that retrospective data collection can be prone to bias.

Remember also that correlation does not necessarily mean causation. This study is saying that exercise was correlated with miscarriages, but one possible explanation for the association could be that women who were destined to miscarry may have suffered less morning sickness and thus were more inclined to exercise strenuously. At present, we simply do not know.

Did Exercise Cause My Miscarriage?

If you have had a pregnancy loss, it is natural to speculate about whether something you did might have caused it, but remember that the majority of early pregnancy losses result from chromosomal abnormalities. Exercise does not change the baby’s chromosomal makeup.

It is unlikely that exercise is a factor in the majority of miscarriages, but it may be a concern for some women. If you exercise frequently or strenuously and you are planning another pregnancy, talk to your doctor about whether you may want to make modifications to your exercise regime in light of the Danish study’s findings.

Sources:

American Pregnancy Association, "Exercise Guidelines During Pregnancy." July 2006. Accessed 29 Sep 2007.

Madsen, M., T. Jørgensen, M.L. Jensen, M. Juhl, J. Olsen, P.K. Andersen, A-M Nybo Andersen, “Leisure time physical exercise during pregnancy and the risk of miscarriage: a study within the Danish National Birth CohortBJOG: An International Journal of Obstetrics and Gynaecology (OnlineEarly Articles). Accessed 29 Sept. 2007.

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