Yes, they can be used, but a cross-trainer is safer than a tread-mill and a stationary cycle is safer compared to a cross-trainer. A tread-mill involves lifting your foot at each step which could sometimes prove a challenge due to your growing belly and limited vision. You do not need to lift your feet each time on a cross-trainer. Thus, it is safer than the tread-mill. Check out Our Portal for more information : www.momandme.in/index.aspx See more..