Hi Leyla, congratulations!
When I had my first son, I went to MNRF in Sept. He was born in Oct. I walked around the whole site, no problem. If you feel up to it, it should be ok. You might feel like you overheat faster, or get tired out faster than usual, so don't overdo it. Of course, the doctor will let you know, too.
An adjustable dress might be a good idea, as well.