International Travel at 29 Weeks

DH and I planned a two week trip to Italy (from the US) several months ago for this coming September. We conceived our first month TTC, which was much sooner than we expected! Therefore, I will be 27-29 weeks pregnant from the beginning to the end of our trip. My major concern is the flights. We had booked exit rows, but because I'm pregnant, we will have to move to regular economy seats. I'm very concerned about being extremely uncomfortable! My OB said that I'll be fine to travel as long as I don't have complications throughout the coming months of my pregnancy. I would feel awful cancelling our trip... it is mine and DH's dream vacation. Advice???