 Hello, I am Dr. Himali Tekani, I am a consultant obstetrician and gynecologist at Manipal Hospital's Old Airport Road, Bangalore. Now as long as the flight cabin remains pressurized, flying is not going to affect the baby at any stage of pregnancy. We do advise you to limit travel by air during the last few weeks of pregnancy because labor can start at any time during this period and that's why it would not be recommended to fly during pregnancy in the last few weeks. Whenever you need to travel by air, you will need to carry all your medical records and all your medications. Certain airlines do ask you to get a certificate from your healthcare provider within the previous 48 hours that you are fit to travel by air and hence you should check with your airline before you embark upon air travel. There may be certain medical problems which do not allow you to travel by air but if you have to be on a flight and it is long, you could walk up and down the aisle in between and not sit at least for longer than 2 hours. Stretching out the legs and doing some ankle exercises would also help and use of elastic stockings would help prevent edema in the legs and clotting of blood in the legs.