Convoy,
I am a female pilot, I work in Europe where the maternity policies are a lot better than they are in the UK.
I'll share my experience with you as it might help your missus.
I am 31, mother of 2 adorable children and 757 captain. I did chose not to fly while pregnant. But some of my colleagues did.
My company supports all its employees through pregnancies, accidents and diseases. (Pregnant women take time off work but so do the men who twist their knee playing football and the ones that cut through their ankle with a chainsaw).
I flew long haul for a while and I must say that I prefer flying short haul as it allows me to spend more time with my family. My partner has a rather demanding job. So short haul is my best option for now.
My advice to your missus would be to chose her job very carefully, there is more than just maternity policies, for example, your job and the amount of time you will be able to dedicate to running the household are to be considered.
Good luck.
LilaJane