Just diving back into the pregnancy pages again in order to write a little essay about flying for the concerned pregnant lady. I keep getting messages from my friends saying 'there's another flying thread on MN again, go and sort it out.' So with any luck, someone will sticky this, or at least remember it is here!
Fwiw, I am a mother of 2 small children and have held a pilot's licence for 16 years, flying large commercial airliners for the last 13 years.
So, some facts.
Firstly, the rules about flying vary from airline to airline, but most of them let you fly as a passenger without restriction until 28 weeks. After that you will need a doctor's certificate saying you are expected to have a healthy and normal remainder of your pregnancy. The reason for the 28 week limit is because there are no facilities on an aircraft to deliver a baby, nor are there any trained staff. Diverting an airliner because someone pops one out at 34 weeks is a costly venture. There is no risk to mother or baby that is not is not also a risk to other passengers - ie you should drink plenty of fluids to keep hydrated and keep yourself moving on a flight to avoid DVT regardless of whether you are pregnant or not. The only things that may impact on you more is if you suffer from morning sickness - you may want to be closer to a toilet in that case. If you are one of the unfortunates who has a miscarriage, flying is not going to trigger this, or make the risk higher, but being on a flight when it happens will increase your distress.
The subject of unpressurised flight occasionally crops up. This requires some common sense. If you are going on a 20 minute seaplane hop in the Maldives, you will not suffer oxygen starvation, nor will your baby. You will not bounce the baby out of your uterus with a water landing. (I was throwing emergency landings in the simulator at 747 pilots up till my 39th week, and failed to bounce the baby out. In fact she had to be prised out by CS 11 days overdue.) If you are planning to fly at 14000ft for a couple of hours, this is a different matter altogether (and would be an issue for the pilot too.)
For anyone who is still skeptical, bear in mind that it is perfectly legal (although unlikely in the UK) for pilots to be flying you around until their 26th week of pregnancy. In the States, many cabin crew fly throughout their entire pregnancies.
Aircraft cabins are pressurised to 8000 feet, meaning that the air pressure in the cabin is the same as it would be outside if you were standing up an 8000ft high mountain. The air is drier than at sea level. Turbulence will not affect an unborn baby.
There are very few noises an aircraft can make that will affect a baby, and generally those noises are crashing kind of noises, in which case you have a bigger problem whether you are pregnant or not!
If anyone has any flying+pregnancy or flying with babies questions, I can generally answer them. Please no 'I'm 12 weeks, is it safe to fly for an hour' types though!