ARTICLE BY JILL BARKER
Although there’s still some controversy, studies show benefits to maternal health
The idea that pregnant women employ caution while exercising is born of the belief that physical activity is harmful to the developing fetus, mother or both. Yet there is very little evidence that exercise is unsafe for either mom or baby.
Still, many women, and some health care practitioners, are wary about exercising during pregnancy.
Some of that concern can be traced back to an overly cautious set of recommendations presented in 1985 by the American College of Obstetricians and Gynecologists, which suggested, among other things, that pregnant women keep their exercise intensity below a heart rate of 140 beats per minute.
Criticized for a lack of scientific evidence and for failing to differentiate between sedentary and physically fit women, the guidelines were modified in 1994 and again in 2002.
The most recent guidelines, the 2008 Department of Health and Human Services Physical Activity Guidelines for Americans, don’t use heart rate as a measure of intensity.
Instead, they recommend that women accumulate 150 minutes of moderate-intensity exercise per week. They also acknowledge a different set of circumstances for physically fit women:
“Healthy women who already do vigorous-intensity aerobic activity, such as running, or large amounts of activity can continue doing so during and after their pregnancy provided they stay healthy and discuss with their health care provider how and when activity should be adjusted over time.”
The Canadian guidelines, published in 2002, are somewhat different still, using heart rate as a guide to intensity but offering two sets of recommendations based on a woman’s level of fitness. They also suggest that sedentary women wait until the second trimester to begin an exercise program.
Michelle Mottola, director of the R. Samuel McLaughlin Foundation Pregnancy Lab at the University of Western Ontario, was instrumental in the development of the Canadian guidelines. According to her, the recommendation was based on the premise that first-trimester fatigue and nausea might cause novices to abandon exercise before making it a habit.
But even that guideline has some wiggle room, provided the pregnancy is without complications.
“If she is feeling okay, even if she has never exercised before, there’s no reason why a pregnant woman (in her first trimester) can’t go out for a walk,” Mottola said.
This plethora of guidelines, combined with past biases, can lead to confusion. And the fact that not all obstetricians are pro-exercise and up to date with the latest research makes it tough for pregnant women to decide which level of physical activity is best for themselves and their baby.
Yet armed with the right information, women can open up a discussion with their physician to create a personalized set of recommendations based on their health and fitness.
One of the best reviews of the benefits of physical activity during pregnancy was published this summer in the journal Medicine and Science in Sports and Exercise. Written by Mottola and colleagues from the U.S. and Norway, Health Benefits of Physical Activity During Pregnancy: An International Perspective synthesized the latest research on exercise and its effects on mother and child. Not only does it offer a wealth of information, it also suggests that exercise is a vital part of maternal health.
According to the review, one of the primary benefits of physical activity during pregnancy is its role in preventing excess weight gain, which Health Canada claims affects 55 per cent of overweight women and 41 per cent of those of normal weight. The consequences of this include an increased risk of gestational diabetes, which has been linked to heavier newborns and childhood obesity.
Women who gain excess weight during pregnancy are also less likely to take it off postpartum. This is especially significant as those extra pounds are not only likely to stick around between pregnancies, but are compounded by more excess weight gain during subsequent pregnancies. Researchers believe this may be the start of the obesity cycle that leads to the birth of larger-than-normal babies who have an increased risk of carrying that extra weight into adulthood.
By contrast, regular exercise during pregnancy increases the chances of delivering babies of healthy weight who are more likely to grow into healthy children. And contrary to old theories, there is no evidence suggesting that exercise will lead to premature births or babies with low birth weight.
That said, there are plenty of unanswered questions regarding exercise during pregnancy. No minimums or maximums regarding the intensity, volume and duration of exercise needed to benefit maternal and fetal health have been established. And there is limited information about the effects of exercise during all three trimesters, which could result in revamped guidelines based on the stage of pregnancy.
Until then, Mottola encourages women to be active during pregnancy. She also suggests they listen to their body and talk to their physician should exercise cause any discomfort or undue fatigue.
“Most of the decisions about exercise pregnancy are common sense,” she said.