In Biblical times, physically active Hebrew slave women gave birth more easily than did their less active Egyptian mistresses.
In the third century BC, Aristotle attributed difficulties in childbirth to a sedentary lifestyle.
Today, scientific data supports this ancient notion that exercise benefits pregnant women and their babies. "Our studies show that women who exercise during pregnancy have shorter labors, gain less fat, require less medical intervention during delivery and recover more quickly than pregnant women who were sedentary," says obstetrician-gynecologist James F. Clapp III of Case Western Reserve School of Medicine in Cleveland.
In 16 years of studying hundreds of exercising pregnant women and their children, he has found that "for most pregnant women, exercise has numerous physical and psychological benefits." Yet during much of this century, active women have been warned to cut back or stop their exercise entirely. Some of these cautions came from societal mores, and some arose from animal studies linking intense exercise with fetal malformations.
Until 1994, the American College of Obstetrics and Gynecology (ACOG) advised pregnant women to limit strenuous activities to no more than 15 minutes in duration and to keep their heart rate to no more than 140 beats per minute.
But in 1994, when ACOG lifted these restrictions for healthy women in low-risk pregnancies, "active women sighed with relief," notes Judy Mahle Lutter, president of the Melpomene Institute, a Minneapolis-based organization specializing in health issues affecting physically active women.
"Many active pregnant women hadn't been discussing their exercise with their obstetricians because they felt their doctors were being unnecessarily restrictive," Lutter says. "This change allowed for a more open and honest exchange."
While most physicians today recognize the health benefits of exercise for women with uncomplicated pregnancies, Lutter says, "there are still mixed messages being given." Many physicians remain overly cautious, concerned that strenuous exercise will harm the fetus.
But one of the first studies to examine the affects of vigorous maternal exercise on humans found "no deficits" in the children. Case Western's Clapp tested the offspring of 20 women who ran, cross-country skied or did aerobics at least three times a week for at least 30 minutes and compared them with the offspring of 20 women who only walked during pregnancy. After testing the children as newborns and re-testing them five years later, Clapp found that children of the mothers who exercised vigorously were as healthy or healthier than the controls.
The study, published in the Journal of Pediatrics, noted that "the exercise offspring performed significantly better" on tests of intelligence and oral language skills. They were also leaner, although their heights and weights were well within the normal range.
"It is not that the offspring of the exercising women are unduly lean at age 5 years," Clapp concluded, "rather that the offspring of the control subjects are a bit on the fat side."
The reasons for these differences are unclear, says Clapp, who suggests one factor may be that exercise stimulates growth of the placenta, making more nutrients available to the baby.
He continues to follow these children and is expanding this research by studying 250 pregnant woman exercising at a variety of different intensities and comparing them to 250 controls. But while he believes in the benefits of exercise for most pregnant women, Clapp won't offer general guidelines for exercise during pregnancy. "This is a highly-individualized matter that must take into account a variety of issues, such as the woman's past conditioning and the status of her pregnancy," says Clapp, who gives detailed advice in his book, Exercising Through Your Pregnancy. "One set of recommendations cannot be used for all women."
In general, today's physicians are "more pro-exercise during most pregnancies," notes Philadelphia obstetrician-gynecologist Mona Shangold, who is writing a patient education pamphlet on exercise and pregnancy for the American College of Sports Medicine. "I tell my patients that it's better to become fit before they become pregnant. But it they haven't already begun to exercise regularly, it's not too late to start."
The Canadian Academy of Sports Medicine released a new position paper on exercise and pregnancy in 1998. Previous advice has been "too restrictive for most women," says physician Julia Alleyne, medical director of the sports medicine clinic at Women's College Hospital in Toronto.
To help doctors determine a safe, individualized exercise prescription, the new guidelines include a screening questionnaire called the PARmed-X for Pregnancy, she notes. It lists certain conditions, such as incompetent cervix or toxemia, that make exercise unadvisable.
Pregnant women should discuss their exercise plans with their health care provider, says Alleyne, who offers this advice from the new guidelines for women in low-risk pregnancies:
- Inactive women may start a program of mild to moderate exercise after their 13th week of pregnancy.
- Active women can continue to exercise at their accustomed level during the first trimester, may increase their exercise slightly during the second trimester and should decrease the level slightly during the third trimester.
- "Perceived exertion" should determine how hard a woman exercises. Previously inactive women should move at a level they consider "mild to moderate" and be able to talk while exercising. Active women can push a little harder, to a level they consider "moderate to somewhat hard," but should avoid exercising so hard that they become breathless.
- Easy endurance activities, such as walking or swimming, are the best choices for previously inactive women. Women who'd been training in jumping or running sports may continue their activity as long as they proceed with caution and check with their physician. But all pregnant women should avoid high-risk sports that could result in falls (like downhill skiing, water skiing and karate) and activities that involve pressure changes (such as scuba diving or mountain climbing).
- Wear good, supportive shock-absorbing shoes.
- Be aware of the "THREE DON'Ts": don't get exhausted, don't overheat and don't dehydrate. Drink 8 oz. of liquids before and 8 oz. after exercise. Choose a sports drink to maximize absorption and supply you and the baby with fluids, carbohydrates and electrolytes. And avoid exercising outdoors in hot, humid weather.
- Remember, too, that the changes of pregnancy can increase your risk of injury, Alleyne says; so be aware that your ligaments aren't as stable and your balance may be off. Also, pregnancy's effects on the body can make heart rate monitoring an inaccurate measure of fitness levels during this time.
- If any of your risk factors change during pregnancy (such as developing elevated blood pressure or gestational diabetes) be sure to ask your physician's advice about modifying your exercise program.