Hi Lolly you sounds just like my best friend . She is now 27 wks but still rides to work each day (about 5kms) and in her 2nd tri did the occassional mountain bike albeit cautiously. But I think her belly has exploded in the last couple of weeks so I am not sure if she will continue the mountain biking, I am sure she will continue commuting though until she doesn't feel comfortable anymore.

Riding is second nature to her but as you know accidents can happen to the best of cyclists so she knows she is taking calculated risks.

Good luck