Well my SO was racing and doing quite well in the Marin Winter Series when she realised there was going to be a little Tasso along later in the year. So had a good nosey around tinterweb and asking many experts in sports science and the like what to do about training, when to stop etc.
Turns out that unsurprisingly there isn’t much real evidence to say what level or type of exercise is good/bad or just ok for preggers people. Prospective mums not being that keen on doing comparative trials to see what’s what.
The first two or three months are probably the most crucial but she continued training and racing through that time and was riding an MTB until very obviously pregnant. This included a tentative descent of the easier sections on the Grand St Bernard with Bike Verbier.
We both think that the high level of fitness helped no end come the birth but we had a few words when she fell off the MTB a few times and she eventually gave in and took it easy with some gentle cyclepath riding.
Ok my wife is probably an extreme basket case but yours should just do whatever she feels comfortable with doing. I’m sure her body will let her know when enough is enough.
I have to concur with GW’s original comment though – that can be as gentle or exuberant as you like and preferably it’s a shared experience good for you both 😉