To prevent oxygen deficit to the fetus, it is essential that any exercise program you design for a pregnant athlete contain a thorough cool-down period comprising gentle exercise. It is also critical that all pregnant clients who exercise at high levels pay special attention to fetal movements in the hours immediately following a workout. Like us, babies stop moving when they are not getting enough oxygen.
Effects of Exercise on the Mother
The three major concerns for pregnant athletes in training are dehydration, hyperthermia and hypoglycemia.
Dehydration. Clapp recommends that pregnant athletes drink sufficient water throughout the day and especially when training. Because blood volume decreases during the early stages of pregnancy, pregnant athletes should drink 6 to 8 ounces of water for every 15 minutes they exercise (Clapp 2002). They should also not exercise when dehydrated. Clapp says one way to tell if they are sufficiently hydrated is to check the color of their urine, which should be almost clear.
Hyperthermia. As mentioned earlier, pregnant athletes should take their temperature (vaginally or rectally) immediately before and after their longest workout (before they cool down).
Hypoglycemia. Blood sugar levels can fall rapidly during prenatal training sessions. Clapp recommends that pregnant athletes monitor their blood sugar levels weekly (using one of the over-the-counter devices that diabetics use). The goal is to maintain a level above 55 to 60 milligrams per deciliter (Clapp 2002).
Whether recreational or competitive, athletes are typically very tuned in to their bodies. Most recognize the signs indicating that exercise intensity levels are too high, and they adjust their workouts accordingly. Pregnant athletes should be encouraged to exercise at a level that feels comfortable, using rating of perceived exertion (RPE) as a guide (Anthony 2002).
A general rule of thumb is that if it feels good, it probably is good; if, however, it feels bad, it's probably not good. Kardel and Kase (1998) studied how high- and medium-intensity exercise affected both the fetus and labor/delivery of the baby. The study involved 42 healthy female athletes who followed either a high- or a medium-intensity exercise program throughout pregnancy until six weeks after delivery. At the end of the study period, there were no differences between the high- and medium intensity exercise groups in terms of onset/duration of labor, baby's birth weight or Apgar score, which measures the baby's health. Once again, such results underscore that healthy, well-conditioned women can exercise during pregnancy without compromising fetal growth and development.
Regardless of fitness level, pregnant athletes should never exercise to exhaustion. According to Clapp, this is less of a concern with recreational athletes. It is more likely to affect competitive athletes, who sometimes use poor judgment with regard to perceived exertion when competing in an event.
Supine Position Caution
Many medical experts caution pregnant women to avoid lying on their backs after the first trimester. Lying in a supine position after the first trimester can put too much pressure on the inferior vena cava (the vein that returns blood to the heart from the torso and legs), owing to the weight of the enlarged uterus. This pressure can lead to supine hypotensive syndrome, characterized by a decrease in cardiac output, blood pressure and fetal blood supply.
Pregnant clients who experience nausea, dizziness or breathing difficulties when supine are most likely victims of this condition and should immediately discontinue lying in this position. However, because only 10 percent of pregnant women suffer from supine hypotensive syndrome, some experts feel that the direction to avoid supine exercise entirely after the first trimester is overly cautious. Clapp, for one, feels that if the legs and torso are moving, interference with blood flow back to the heart should not be a problem (Clapp 2000).
A more moderate recommendation that I make--only to my asymptomatic clients--is to limit the amount of time spent in a supine position to just a few minutes of each workout. Women who continue to do supine abdominal crunches after the first trimester should be aware of the potential for diastasis, a condition in which the rectus abdominis muscle separates at the linea alba.