Fitness for mothers to be

by Deborah Kallen, M.S.

With the increased interest in physical fitness that flourished in the 1980s, medical researchers had to take a closer look at the effects of exercise on pregnant women, many of whom wanted to maintain their fitness programs during pregnancy. What resulted was an abundance of data suggesting that women's bodies have natural built-in biochemical strategies to maintain the health of a growing fetus while under the stress of strenuous exercise.

Evidence is mounting that pregnancy is no excuse for a woman to give up regular physical exercise. In fact, much of the medical research looking at the effects of exercise on maternal and fetal health shows that active pregnant women are in better shape than their sedentary counterparts. They are more aerobically fit, have better muscle tone, and gain less weight from fat during their pregnancies. They run no greater risk of miscarriage and their babies are just as healthy.

The research has been so convincing that in 1994, the American College of Obstetricians and Gynecologists (ACOG) loosened their rather stringent exercise guidelines for pregnant women. The newer guidelines now affirm the safety of moderate exercise during pregnancy and postpartum "in the absence of either obstetric or medical complications."

Prior to 1994, the ACOG advised limiting strenuous activities to no more than 15 minutes at one time and at a maternal heart rate less than 140 beats per minute. If a pregnant athlete adhered to this restrictive formula, it would preclude her from training for an upcoming event and, more than likely, lower her overall fitness level.

What the newer standards suggest is that a woman's nonpregnant fitness condition and stamina should be a key factor as she and her doctor determine a safe exercise regimen during her pregnancy. The same exercise that may drive the heart rate of a chronic couch potato to dangerously high levels may hardly get a seasoned athlete's blood pumping.

Mary Davies is a 45-year-old Millville, NJ triathlete ranked among the ten fastest women in the world within her age range. She considered her three pregnancies a time for her body to rest. "Pregnancy takes me down a peg or two," she said.

Davies' exercise program may seem relaxed to her. But it would be a grueling and unattainableable athletic challenge for most women - and men, for that matter. During her pregnancies, Davies ran an eight and a half to nine- minute mile compared to a seven and a half minute-mile when she's not pregnant. She also shortened her distance running routine - from six to seven miles three days a week when she's not swimming or cycling, to three to five miles.

The experts say that exercise is okay for women at the other end of the fitness spectrum as well. Even women who were completely inactive before getting pregnant can benefit from exercise. But the experts recommend that women who fall into either of these categories must work into an exercise routine slowly. And pregnancy is certainly not the time to take on a new sport or major body conditioning goals.

Swimming and stationary cycling are great ways to get ready for the real marathon-- labor and delivery-- because they're noncompetitive, non-weight-bearing, and involve smooth, nonjarring movements.

The body operates differently when it carries a fetus than when it does not. Given this knowledge, it would seem logical that a woman's response to exercise would probably also be different. But prior to the 1980s there was little clinical data to back up this assumption. Therefore, doctors took a conservative approach with their pregnant patients, emphasizing limits and caution.

However, when interest in health maintenance and fitness began to surge more than a decade ago, the need for definitive answers grew. By then, fifteen percent to twenty percent of women in their child-bearing years were regularly in the gym or on the track. For the most part, these women didn't want to cut down on their exercise after they were pregnant. But they did want to ensure the health of their growing babies.

Fortunately, the questions they brought to their doctors stimulated a flood of new research on exercise during pregnancy. Now doctors have more clinical guidelines to help them prescribe safe exercise for their pregnant patients.

What the research showed was that the body, a truly amazing machine, makes adaptations in its pregnant state to preserve the health of the fetus. And strenuous exercise often plays an added "feto-protective" role.

For example, during pregnancy the amount of energy used by the body to keep the heart beating, the lungs expanding and contracting, and the muscles flexing is greater than during nonpregnancy. This higher basal metabolic rate is related to a generally higher body temperature in pregnant women.

Clinical studies had suggested a higher risk of neural-tube defects, such as spina bifida, when the mother's internal body temperature rose above 102.5 Fahrenheit. Therefore, overheating the body during strenuous exercise was a legitimate medical concern. Researchers then went about measuring temperature changes in pregnant women during exercise.

What researchers discovered was that pregnancy enhances the body's ability to dissipate heat - and so does strenuous exercise. Dr. James E. Clapp III, MD, one of the foremost researchers in the field of maternal exercise and pregnancy, was able to show that heat stress on fit mothers-to-be during endurance exercise is reduced by 30% in early pregnancy and by 70% in late pregnancy.

A woman's circulatory system changes with pregnancy, too. Blood volume increases by about thirty percent to accommodate the growing fetus, the heart pumps more blood per beat, and blood flows more easily throughout the body.

Despite this increased blood volume, early clinical research on exercise and pregnancy determined that strenuous exercise decreased the amount of blood flow to the uterus and the growing fetus. But they hadn't demonstrated that this damaged the fetus in any way.

In the early 1990s, a study done at Texas Children's Hospital and Baylor College of Medicine showed the extraordinary compensations the body makes when a pregnant woman exerts herself. They took a variety of cardiac and respiratory performance measurements in physically active subjects and sedentary subjects, all of whom were pregnant. The measurements were taken over several months at a given heart rate for all subjects.

The researchers found that the hearts of the aerobically fit women pumped a greater volume of blood than did the hearts of inactive women. Their bodies also used a greater percentage of the oxygen from that blood for the necessary nourishment of body tissue. Even if the earlier studies that showed decreased blood flow to the baby during exercise could be repeated with the same results, the Texas research demonstrated that increased oxygen uptake kept fetal oxygenation relatively constant.

But along with the green light much of the recent research on exercise and pregnancy has given to recreational and competitive athletes, there are also several caveats.

Don't exercise on your back during the last two trimesters of pregnancy. One of the changes in circulatory function not mentioned above is that when a pregnant woman lies on her back during this time in her pregnancy, her heart pumps significantly less blood. Exercising in this position could cause dizziness and diminish blood flow to the fetus.

Don't stand in one position for extended periods of time. This will result in a marked decrease in blood flow - more marked than when lying on your back.

Be aware that as your body shape changes, so does your balance, especially in your final trimester. Exercises that require good balance, like tennis or dancing, require more-than-normal caution. .Be aware that most of the body changes you experienced during pregnancy extend 4 to 6 weeks into the postpartum period. Take the same precautionary measures that as you did before your baby was born.

Be careful not to become overheated. Layer your clothes so you can easily shed them if you get too hot. Wear breathable clothing, such as cotton. Exercise during the coolest part of the day. Drink plenty of water or other caffeine-free liquids, especially during and right after exercise.

Never exercise to the point of exhaustion. Listen to your body and stop when fatigue sets in.

Avoid any sport or exercise that could result in accidental trauma to the stomach. Skiing, roller blading, or surfing are three good examples.

If you want to keep in shape during your pregnancy, do it regularly. Exercise done at least three times a week is better than sporadic exercise.

Make sure you give yourself 5 minutes of warm-up exercises at the beginning of your more strenuous workout. Follow your workout with 5 minutes of cool-down exercises. This will protect your joints, which are more prone to injury during pregnancy.

Be aware that pregnant women who exercise need about 300 more calories than sedentary pregnant women. Your goal should be to gain between 25 and 35 pounds before you deliver your baby.

Stop exercising and consult your doctor if you experience shortness of breath, vaginal bleeding, vaginal water leakage, stomach pain, dizziness, nausea or tingling sensations.

Above all, discuss your exercise plans with your doctor and make sure you have no contraindications for exercise. These would include pregnancy-induced hyertension, premature labor during a previous or your current pregnancy, a condition known as incompetent cervix, persistent vaginal spotting or bleeding, or evidence that your baby's growth is below average.

If a woman pays attention to the signs her body provides, evidence suggests that exercise during pregnancy can have many side benefits. It may lessen the discomfort of swollen feet and legs or the severity of varicose veins, increase your sense of well-being, and add muscle rather than fat weight to your growing body. And last, exercise will prepare you for the workout ahead during labor and delivery.

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