If your already used to being active it's not going to hurt the baby :)
Agree with the above post ^^^^^. You should be fine. I'm 35 weeks and I still bike ride. Talk to your Dr and follow what your body's telling you. If your body feels like it's too much then back off a bit but as long as your not over forcing yourself you should be fine.
I'm 30 weeks pregnant n still bike riding.. at 25 weeks I stop my 3 miles runs just because it was making my husband uncomfortable not because I couldn't run anymore. Doc said that anything exercise wise I was doing b4 i should be fine doing while pregnant. So I continued n feel great afterwards.
15 miles is kind of a lot so I'd check with my doctor first to be safe