Exercise During Pregnancy
The impact of exercise on the pregnant woman and her fetus has been the source of considerable debate resulting in conflicting recommendations. Physical fitness enthusiasts have championed maintenance of a high level of activity during pregnancy, whereas others, particularly those concerned with the effects of physical labor in the work environment, have voiced caution. Usual advice to pregnant women from the obstetric community has been to decrease activity and increase periods of rest, particularly in the later months of pregnancy. Over the last decade, a number of studies have been conducted regarding this issue. Unfortunately most have been of weak scientific method and reflect the bias of the investigators.
The following is a composite of published recommendations for exercise during pregnancy:
To appropriately achieve the benefits of a training program, particularly its cardiovascular effects, exercise should occur on a regular basis. Three times a week for 20 to 30 minutes is minimally adequate. Sporadic intense exercise is to be avoided.
The intensity of exercise should be such to attain at least 60 percent of maximum heart rate. At the same time, women should avoid anaerobic exercise or exercising to maximum heart rate. Good guidelines include that a woman's heart rate during exercise should be above 120 beats per minute and below a maximum level. Recommendations for the maximum level generally are in the range of 140 to 150 beats per minute. A practical guide is that easy conversation should be possible at all times. Full recovery from exercise as judged by return to pre-exercise heart rate should occur within 15 minutes after each exercise session. Multiple exercise sessions of shorter duration are preferable to longer sessions. Particularly ones lasting more than 30 minutes. During the last trimester, and particularly the last month, the intensity of exercise should be reduced markedly.
Appropriate warm-up and stretching of the ligaments and muscles is important to prevent injury. On cessation of exercise, a gradual slowing with some leisurely walking or elevation of the legs will help venous return and prevent dizziness. The supine position should be avoided; lateral recumbency is the position of choice for prevention of syncope.
Exercises using large muscle groups, particularly those that are rhythmical in nature, such as walking, jogging, swimming, cross-country skiing, and bicycling, are to be encouraged. Those that require increased balance and coordination or those that involve the potential for injury, falls, or blows should be modified or avoided. Exercises (such as certain weight-lifting routines) that strain the lower back and use Valsalva's maneuver should be modified or avoided.
Adequate breast support with non-stretchable straps will aid in comfort and prevent stretching of Cooper's ligaments of the breasts.
Exercising in heat should be avoided. Hot tub and sauna bathing should be limited to five to 15 minutes.
Adequate diet, particularly carbohydrates intake, should be maintained.
Any condition that compromises uterine oxygenation should lead to discouragement of exercise. Contraindications to exercise include medical problems, such as cardiac or pulmonary problems and anemia, or obstetric conditions, including bleeding during pregnancy, diabetes, hypertension or preeclampsia, premature labor, multiple gestation, previous intrauterine growth retardation (IUGR), recurrent miscarriage, or history of premature labors.
The woman and the professional caring for her should discuss and agree upon the physical fitness program. Short term studies have noted transient fetal heart rate abnormalities during and after exercise.
It is prudent to advise women not to engage in very vigorous conditioning exercise during the third trimester.
The woman should resume exercising gradually during the postpartum period. If increase in fatigue levels, pain, or bleeding occurs with exercise, the woman should postpone increasing her physical activity. Lactation is not a contraindication to exercise; most women will find exercise more comfortable after nursing so that the breasts are not full. Exercise in the heat while nursing may lead to dehydration and decreased milk supply. Adequate oral fluids are essential.