By the third trimester, you’ll be carrying considerably more weight as your developing baby grows. It’s almost inevitable that as a result you’ll feel more tired and it may be awkward to exercise with your bump. Although research has found that continuing to exercise during pregnancy isn’t harmful, you may find that aerobic activity isn’t practical. If you can, try to keep up some stretching and relaxation exercises.
There's long been documentation that exercise during pregnancy has its benefits. Paul Sorace, MS, Fellow of the National Board of Fitness Examiners and a teacher at the American Fitness Professionals and Associates, lists the following:
Whether exercise is harmful or whether it improves the course and outcome of pregnancy is largely unknown. Therefore, no definitive recommendation can be made to promote exercise during pregnancy. Nevertheless, there appears to be no reason that most women cannot continue with exercise during pregnancy and reap the possible benefits of improvement in well-being.
Some studies have demonstrated possible benefits of exercise during pregnancy. An example is the trend toward shorter labor and less need for intervention in well-conditioned and highly trained women. This benefit is difficult to establish as a result of exercise alone because exercise is associated with multiple positive cofactors such as better nutritional status and avoidance of tobacco and caffeine. Although variations in study results are noted, the physical conditioning of the subjects as well as the type and timing of exercise may explain some of the discrepancies.