Pregnant athletes should be able to continue their strength training routine throughout pregnancy. They ought to breathe normally during strength training because any act of breath holding (as during a Valsalva's maneuver) can reduce oxygen delivery to the placenta.
To keep the oxygen supply going to the fetus, pregnant clients should avoid maximal lifts and heavy resistances, especially when increasing amounts of the hormone relaxin are present (see next section).
Although ACOG guidelines recommend a single set consisting of at least 12 to 15 repetitions (without undue fatigue) for each resistance exercise, I have found that pregnant athletes can safely perform up to four sets of eight to 10 reps (again, without undue fatigue).
Experts generally advise that all pregnant exercisers--regardless of fitness level--avoid stretching to maximal tension, because of relaxin's effect on the joints. The purpose of relaxin is to provide increased movement in the pelvis to accommodate the growing baby and allow for an easier birth. It helps the abdominal muscles stretch during pregnancy and the pelvic floor muscles stretch during delivery. Relaxin concentrations are greatest in the first trimester, drop after the fourth month and then reach a second peak prior to labor (Anthony 2002).
Although relaxin is no longer manufactured in the postnatal period, its effects on the ligaments and joints linger on until about 5 months after delivery. Because there is no objective evidence that relaxin production leads to injuries when stretching, Clapp says there is no reason for pregnant athletes to change their flexibility routines during pregnancy (Clapp 2002).
This is another situation in which clients should know their bodies and their limits. However, to be on the safe side, ballistic stretching is definitely not recommended during pregnancy, to avoid the potential for muscle tears.
Blood volume increases dramatically during pregnancy; while vasodilation increases to accommodate this blood flow, blood pressure can be inconsistent during the first two trimesters. As a result, heart rate is a poor indicator of exercise intensity during pregnancy. Therefore, pregnant athletes should know how to assess their own intensity using the RPE scale.
As mentioned earlier, ACOG advises against exercising to exhaustion, regardless of fitness level. According to the American College of Sports Medicine, pregnant women can continue to exercise at high intensity levels as long as they do not exceed their pre-pregnancy intensity levels (ACSM 2000).
Pregnancy and Sports Participation
Recently, there has been much controversy about the role of pregnant women in sports. Experts in the fields of medicine, law, insurance and ethics presented current research, statistics and information relating to this topic at the National Forum on Pregnancy and Sport conducted in Sydney, Australia, in 2001. The following is a brief summary of the key points made by the medical presenters (SMA 2001):
- Medical evidence suggests that healthy pregnant women (with normal pregnancies) can participate in sports without affecting the course or outcome of the pregnancy. (The panel did make some provisos in terms of type, intensity, duration and frequency of exercise.)
- Pregnant athletes should avoid maximal-intensity exercise, have a thorough cool-down period of gentle exercise, avoid excessive stretching and jerky ballistic movements, ensure adequate fluid intake, and pay attention to core body temperature.
- The fetus is extremely well protected from blows to the abdomen during the first trimester (first three months) of pregnancy.
- The risk of abdominal injuries during sports (for both men and women) is extremely low. Current research indicates that fewer than two percent of all injuries, including those that occur during contact sports, involve the abdomen or chest area.
- The pregnant woman, herself, is best placed to know (generally from discomfort and lack of coordination) when to stop participating.
- Pregnant women should seek advice from medical professionals and, if appropriate, seek a second opinion.
- No medical evidence has linked adverse outcomes for the fetus (including miscarriage) to sporting injuries. Statistics and research on adverse outcomes following severe or catastrophic trauma to pregnant women relate almost exclusively to road trauma and domestic violence.