You should tell your employer as soon as possible and if he/she is understanding they would still go ahead with the visa formalities.

On ther other hand I personally suggest not telling them and let them proceed with the visa formalities. And when they get the visa let them know about it. Then they would not be in any position to create problems.

I remember reading somewhere that Qatar Labor Laws state that the pregnant woman is entitled to two months paid leave. You can send a query to the Gulf Times and hopefully you will get the answer very soon.

In any case I wish your upcoming baby is healthy happy intelligent and gets the utmost care...