A: In general, exercise is safe and recommended during pregnancy. For many pregnant women, swimming is favored because there is no additional stress on already-sore joints. There are a few exceptions, however. Women should not begin any new exercise programs during pregnancy unless they are specifically designed as pregnancy classes. For example, women who routinely run prior to pregnancy can continue to run, but women who haven't run routinely prior to pregnancy shouldn't take up it up during pregnancy. Also, exercise that can result in sudden falls (rollerblading, mountain biking, etc.) should be avoided even if they were done prior to pregnancy.