Good question. I'll be traveling soon too, and I feel like the only reason doc wouldn't let you travel is fear of you going into early labor.
I plan on traveling by vehicle to Georgia from Michigan for my family's annual thanksgiving gathering and I'll be 28 weeks; however, my doctor did tell me that even though I have a normal healthy pregnancy. ..I should not be traveling anywhere beyond 34 weeks. I Don't know if each doctor has a different recommendation or not but this is what mines just stated this past week.
Depends on how far along you are.
As long as you are not high risk and get the ok from your doctor. Usually they recommend not traveling after 36weeks...