Liz, long range flights, I hate to say it, are not a good idea when you are pregnant... I know so many people say and think it's ok, but you make some enquiries how many Mums had premature deliveries following a long haul flight, and you would be shocked. Most midwives know this but are often not allowed to say, the doctors are allowed to say but mostly don't, as it seems unwelcome news, or they just don't know or make the connection.
With babies and travelling, not too young but before walking or crawling age is safer, as you have so much more control over what they touch and put into their mouths. I think it's a sign of what a great Mum you are going to be if it worries you, much much better to be safe than sorry, some things are not worth the risk. I took my boy to Rome when he was 6 months old, that was fine, he was a robust healthy little boy, too, so there is the argument that you will be the best judge when the time comes, it will depend if your little one is robust in general. I keep tinking about a little girl when I think of you and babies....