Benefits of exercise
According to authors of the study, health authorities in the US, Great Britain, Norway and Denmark recommend a level of physical activity for pregnant women similar to that of women who aren't pregnant. These recommendations are based on the health benefits of physical activity for the mother, including a healthy weight and prevention of gestational diabetes and preenclampsia. However, whether this is good for the fetus is unclear.
Exercise and preterm birth
The study also states that almost all attempts to prevent or predict preterm births have failed and that the incidence even seems to be increasing in some countries, particularly the US and Denmark. Some research suggests that chemical changes that occur during exercise could theoretically induce preterm birth but other research shows contradicting results.
Authors of the study chose to examine over 87,000 pregnancies included in the Danish National Birth Cohort between 1996 to 2002 to determine if exercise helped or hindered women in having full-term pregnancies. Women were asked about their exercise habits, including how many hours per week, the types of exercise performed, intensity of exercise, and changes in exercise habits from early to late pregnancy.
Results of the study showed a reduced risk of preterm birth among the almost 40 percent of women who engaged in some kind of exercise during pregnancy in comparison with nonexercisers. However, there was no dose-response correlation, meaning there was no relationship between the amount of time a pregnant woman exercised and preterm incidence. Further, the type of exercise did not correlate with whether or not a pregnant woman carried to full-term or had a preterm birth.
Of the women in the study, nearly five percent had preterm births. Sixty-three percent of the pregnant women did not exercise at the beginning of their pregnancy and by the end of pregnancy, 70 percent of the women were not engaging in regular physical activity. (That's a lot of women choosing to forgo exercise while pregnant.)
Among the women who did exercise (a little more than one-third of the moms-to-be), exercising more than two hours per week was infrequent, and in late pregnancy approximately half of the active women exercised for only one hour per week or less. Among physically active women, the most common activities were swimming, low-impact activities, and bicycling – yet, all types of exercise were associated with a reduced risk of preterm birth (except for horseback riding, which is considered risky during pregnancy).
The findings indicate either that physical exercise is associated with a reduced risk of preterm birth or that women with a low generic risk of preterm birth are more likely to be physically active, referred to by researchers as a "healthy exerciser effect."
Regardless, this study suggests that any type of physical activity (deemed safe for pregnancy) can improve a woman's chances of having a full-term birth. Also, the amount of time spent on exercising is not the crucial component – simply getting up and doing something is the real key.
Researchers conclude that their findings do not indicate any adverse effects of exercise on the risk of a preterm birth and do not conflict with the current recommendations. In addition to the health benefits of exercise during pregnancy, light to moderate exercise can make you feel better as well as prepare your body for the rigors of childbirth. Even better, the more fit you stay while pregnant, the quicker your postpartum recovery and getting your pre-pregnancy body back.
Visit the American College of Obstetricians and Gynecologists website for guidelines on exercise during pregnancy
Physical activity may reduce risk of gestational diabetes
Exercise tips for pregnancy
Pregnancy and heart rate