Hm, it really does depend a lot!
I'm working for a big British low cost airline and the maternity deal is one of the best ones around.
As soon as you suspect you may be pregnant you'll be grounded (in the sense that you aren't flying but there is no ground jobs either) and then, until normal maternity pay kicks in (I believe 2 weeks before your due date) you'll get paid the average pay of your past three pay checks (something like that).
So basically you are on full pay, and you don't work!
Pretty good deal, if you ask me.
Not sure which country you are from and which airline you are working for but my first suggestion would be to join a Union....if available.
If worst comes to worse....your babies health is more important than anything!!! Screw the job, walk out, and have a happy, healthy baby instead!
Of course I don't know if you can but that would be my advice, and it would be what I would do, if I could!
Just my opinion.
Good luck with your fight for your rights, and all the best for your pregnancy :-)