If you have a regular gyn or FP/GP doc, I'd ask him or her; like asking the orthopedic surgeon about training after an accident, I'd go with a book of pictures or loose clothing in which to demo what it is goes on in class. We're used to helping women plan ahead these days, but everyone is different so there are not a lot of hard and fast rules. Falling/breakfalls etc would probably be out regardless.
Another thing to keep in mind, are you prone to reaching for Motrin after class---you will be limited in what you can take for pain once pregnant, so may not want to do too many things that will make you wish you could take medication.
Also, sad to say, but many folks insist on training when ill, rubbing their viruses all over their partners
. Sigh. Again, not ideal when you are trying to stay healthy for the baby...