i just wanted to come on and share my story since I read so many of yours while I was going through this. Maybe this will help someone.
I discovered an osteochondroma on my ankle a few years ago. I had an MRI and a CT scan and was told it was nothing to worry about. for the past year or so it has been bothering me more and more. My leg was sore a lot after activity like dancing and I knew it was all of the muscles around the osteochondroma. I went to my orthopedic doc and got an X-ray and he told me it had grown. he said I would need a biopsy and a bone scan to check for cancer because if it grows unexpectedly in adulthood it is very likely cancer. He also told me he could just remove it because it was causing pain. The only thing my doctor said that put me at ease was that it could have possibly been my recent pregnancy that caused it to grow.
So I scheduled my surgery and went home terrified. The internet did not put my mind at ease because I couldn't find anyone whose pregnancy caused their osteochondroma to grow. Everything I read was "if it grows in adulthood its cancer". I cried for a week until my surgery, and then for the following 5 days waiting for the pathology results. I had completely convinced myself I had cancer since I couldn't relate to any of the situations I read on the internet.
I got the results back and it was totally benign! I just wanted to get my story out there incase there is another woman who had a baby who was going through this. Obviously, if your osteochondroma grows you should have it biopsied or removed, but its totally possible that it's benign. hormones can do crazy things!!!