By Judith Brown, R.D., M.P.H., Ph.D. WebMD Medical Reference from "Nutrition & Pregnancy: A Guide from Preconception to Postdelivery"
Reading is to the mind what exercise is to the body.
-- Sir Richard Steele, 1712
Regular exercise is something many women do not want to give up and that other women want to take up during pregnancy. Unfortunately, deciding what to do about prenatal exercise can be troublesome. Women who seek out opinions on the safety and benefits of regular exercise in pregnancy hear both enthusiastic reports of its benefits and stern warnings about its dire consequences. What is the scoop on exercise in pregnancy? Is it safe and beneficial for mother and baby, or might it be hazardous? This article addresses the current status of knowledge about and recommendations for exercise in pregnancy, and answers questions women frequently ask about this topic.
Overview of Exercise in Pregnancy
About 42 percent of pregnant women in the United States exercise, and most of these women walk, swim, or participate in other aerobic exercises. In general, women avoid heavy physical activity and reduce their levels of exercise as pregnancy progresses. Pregnancy physical activity routines are often modified due to changes in balance, the increase in blood volume (which can cause women to tire more easily), the presence of nausea and vomiting and other discomforts, and weight gain. Levels of physical activity generally rise again after delivery when there is a new baby to care for and a drive to get back into shape. Activities that "feel right" often include:
walking
swimming
stretching
golf
Frisbee
tennis
floor exercises (aerobics, stretching, and front- and side-standing leg lifts)
Effects of Exercise During Pregnancy
Both the potential benefits and hazards of exercise in pregnancy have been overstated in the past. Current evidence indicates that regular physical activity in healthy, well-nourished women is safe and may be somewhat beneficial. Women who exercise moderately and regularly tend to experience fewer of the normal discomforts of pregnancy and benefit from the sense of well-being regular exercise can bring. Women who consume a healthy diet, gain weight at the recommended level, and avoid activities that are too intense or may cause injury should not worry that exercise will harm their baby.
There are some women for whom exercise during pregnancy is a matter for concern. Exercise may not be advised for women who fail to gain weight, or who have preeclampsia, premature rupture of the membrane, hypertension, heart disease, preterm labor, second or third trimester bleeding, or a weak cervix. Pregnant women should also be sure to exercise moderately, and not "overdo it."
The Upper Limits of Exercise During Pregnancy
Excessive levels of physical activity in pregnancy can reduce fetal growth and increase the risk of preterm delivery. A cardinal sign that exercise level is too high is a low rate of weight gain. Exercise or physical activity that ends in exhaustion, endurance activities, and activities undertaken in hot, humid climates should be out-of-bounds for pregnant women.
Recommendations for Exercise in Pregnancy
The American College of Obstetrics and Gynecology and other groups have studied the benefits and hazards of physical activity in pregnancy and developed recommendations for exercise. These recommendations are highlighted in Table 8-1.
Current recommendations for exercise in pregnancy are less restrictive than in the past and reflect the conclusion that moderate levels of physical activity by healthy, well-nourished women pose no special risk to pregnancy. Pregnant women should exercise moderately, or at 50 to 60 percent of maximal heart rate for twenty to thirty minutes three times per week. Maximal heart rate, or MHR, represents your maximal oxygen utilization level, or VO2 max. Maximal heart rate represents the highest number of times your heart can beat per minute during periods of highly intense exercise. Brief bouts of exercise at 70 percent of MHR are considered okay. You can estimate your MHR from your age: 100 percent of MHR is estimated as 220 minus a person's age. (This formula may be somewhat undependable for pregnant women, who tend to have a higher heart rate than nonpregnant women.) To calculate 50 percent of MHR for a thirty-one-year-old, for example, you would subtract 30 from 220 and multiply the results times 0.5:
220 - 30 = 190
190 x 0.5 = 95 beats per minute
Exercise that results in a heart rate of 95 beats per minute would approximately equal 50 percent of MHR. To see if you are exercising at this level, you need to take your pulse and determine how many times your heart beats within a minute. Usually people count the number of pulses in ten seconds and then multiply that figure times 6 to calculate beats per minute.
Specific concerns about what exercises or levels of physical activity are safe and questions about how the presence of certain physical problems relate to exercise in pregnancy should be brought to the attention of your health care provider.
Table 8-1: Recommendations for Exercise in Pregnancy
The Dos
Do exercise moderately and regularly unless otherwise advised by your health care provider.
Do emphasize non-weight bearing activities and those that don't require a keen sense of balance.
Do wear loose-fitting, lightweight clothing that allows heat to escape and moisture to evaporate.
Do drink plenty of fluids during exercise; eat appropriately.
Do consume a healthy diet and gain weight as recommended.
Do exercise at 50 to 60 percent of maximal heart rate (or VO2 max)
The Don'ts
Don't exercise or perform physical work to exhaustion. Quit when you feel tired.
Don't exercise while laying on your back in the second and third trimester.
Don't exercise in hot, humid conditions.
Don't perform activities that may traumatize the abdomen or uterus or cause you to lose your balance.
Don't fast or exercise while you are hungry
Questions about Exercise and Pregnancy
Q. Can I alter my physical activity level to help manage my weight gain?
A. Yes. Increasing low levels, or decreasing high levels of physical activity helps some women achieve the recommended weight-gain goals. Intense exercise should not be used, however, to lose weight. Weight loss is never recommended in pregnancy.
Q. Are high levels of physical activity harmful to the baby?
A. They can be harmful if too much of the mother's energy supply is going to fuel exercise and too little is available for the fetus. Blood glucose levels drop more quickly with exercise when women are pregnant because of fetal demands for glucose. Blood and oxygen supply to the fetus may be compromised when women exercise strenuously or undertake endurance events. Exercise in hot, humid climates may lead to overheating and dehydration, both of which can be harmful to both mother and baby.
Q. If I exercise during pregnancy will my labor be shorter?
A. There is no clear answer to this question. Although it does not appear that exercise during pregnancy is related to longer labors, it is not clear that it decreases the length of labor.
Q. Is there any harm in not exercising during pregnancy?
A. Women who don't exercise during pregnancy may experience more of the aches and pains that can accompany pregnancy and may tire more easily than women who exercise regularly. Otherwise, few differences in physical health have been observed between active and sedentary pregnant women.
Q. Are there particular exercises I should avoid during pregnancy?
A. Highly strenuous exercises, those that require a keen sense of balance, and exercises that may traumatize the uterus or abdomen should not be undertaken. This eliminates endurance events, hauling heavy objects, water skiing, scuba diving, surfing, inline skating, ice skating, downhill skiing, horseback riding, sit-ups, push-ups, toe-touches, and field hockey and other contact sports.
Q. Exercises I used to do all the time are more difficult now that I'm pregnant. Is that normal?
A. Yes, it's normal. Many women tire more easily from physical activity, especially during the first few months of pregnancy. Added blood volume, more weight, and shifting balance all contribute to making exercise harder when pregnant. If you tire very easily or feel fatigued most of the time even though you are getting a good night's sleep, make sure you don't have anemia. Have your health care provider check for it.
