How can i maintain my cardio fitness while avoiding accidents during my second and third trimesters?

Swimming: Swimming is a great exercise as you get farther along in a pregnancy. Aside from being an excellent form of cardio fitness, it is less traumatic on the body and the buoyancy makes it easier to exercise with the extra weight that comes with the pregnancy.

Taking it easy!: Your ob/gyn is, by far, the best person to answer this type of question.

Variable: If you have achieved an extremely high level of fitness including high impact exercises, you might not be able to do this. I know of runners who still ran, though a little slower, almost to their delivery date. Much depends on you and your routine and anatomy/physiology. Swimming , reclining cycle, treadmill or outdoor walking. If a runner, see how it goes. May want to wear something, in case.