I'm in the same boat as you. As far as I am aware there is nothing wrong with the actual "RIDING", it's the falling off you need to worry about. So I have given the mountain biking a miss and just go for a ride around the local streets where there is little traffic.

The main reason I gave up mountain biking is because I know that when I don't feel confident, that is when I fall off. So being pregnant I would be worried and therefore fall off where I wouldn't normally.

Great to see that you are not letting yourself become an invalid whilst you are pregnant. Good on you!!!