Professional opinions on the effects of heavy exercise on the incidence of pregnancy are divided. Most health care professionals agree that light to moderate exercise is beneficial to the expected mother and the infant upon birth. However, heavy exercise may be associated with an increased risk of miscarriage. Consult with your obstetrician before engaging in any form of new exercise protocol.
Intense exercise
Medical research on the effects of heavy exercise during pregnancy is limited, but several studies have shown that intense exercise may be harmful and cause miscarriages. An article published in the March 2005 issue of "The Journal of Reproductive Medicine" reviewed current medical studies and revealed that moderate exercise for a low-risk pregnancy was relatively safe and improved maternal physical and psychological fitness. However, the authors found that data on the impact of exercise during pregnancy is conflicting and suggested further studies.
Incidence of Miscarriage
A study included in the September 2008 issue of a Danish medical journal, "Ugeskrift for laeger (Weekly Journal for Physicians)," evaluated the effects of exercise on the incidence of miscarriages. The researchers interviewed more than 90,000 previously pregnant women through telephone interviews and found a relation between the frequencies of exercise and the risk of miscarriage. The authors stated that high-impact exercise was associated with increased miscarriages, but no association was found after 18 weeks of gestation.
Preterm Delivery
The Danish Institute of Public Health examined the correlation between physical exercise and the risk of preterm delivery and miscarriage. The researchers gathered information from more than 87,000 women concerning the hours of exercise per week and the type of exercise in which the women were engaged. The study found women that exercised minimally had a nearly 40 percent reduction in the incidence of pregnancy complications compared to those not exercising during pregnancy. There was no correlation between the type of exercise and the incidence of miscarriage.
Duration of Exercise
The July 2006 edition of the "Australian and New Zealand Journal of Obstetrics and Gynaecology" examined whether vigorous exercise was correlated to reduced birth weight and length of pregnancy. The researchers recruited 148 women for the study, who completed questionnaires on exercise patterns during each trimester of pregnancy. The study found no significant differences between the types or duration of exercise, the trimester during exercise, nor the incidence of preterm delivery or miscarriage.
References
- "Australian and New Zealand Journal of Obstetrics and Gynaecology"; Vigorous Exercise and Birth Outcomes in a Sample of Recreational Exercisers: A Prospective Study across Pregnancy; Duncombe, et al.; July 2006
- "American Journal of Epidemiology"; Physical Exercise during Pregnancy and the Risk of Preterm Birth: A Study within the Danish National Birth Cohort; M. Juhl, et al.; February 2008
- "Weekly Journal for Physicians"; Leisure Time Physical Exercise during Pregnancy and the Risk of Miscarriage: A Study within the Danish National Birth Cohort--Secondary Publication; M. Madsen, et al.; September 2008
- "The Journal of Reproductive Medicine"; Exercise during Pregnancy: A Critical Appraisal of the Literature; S. Morris, et al.; March 2005
