Yes, it's not good to travel if u r already 6month gestation!!
but, by the way it's really cheap if u buy the BB product in Japan. I just brought a carseat combi only Y7980 (for kids not for BB). The carseats are v. cheap. I went to Hokkaido, Bestom, akachan,and 'Sei Chun Hok' are good, esp there sale items.
Maybe u can plan the trip after the delivery la..........safety is most important ar!!