Congratulations for trying! How excited you two must be to try having a baby.
I am going to give you medical advice, being I am a nurse. First of all, I would check with your OB/GYN doctor once you have conceived to make sure it is all right to do belly dancing while pregnant. For most women, it is perfectly safe and good for them to do belly dancing. If there are any complications such as bleeding and certain other pregnancy complications, your doctor may advise you not to do dancing. (This did happen to a friend of mine.) Keep in mind, these occurances are rare.
While dancing, make sure to take it easy and not dance until you tire yourself out. Keep hydrated and rest if some moves makes you feel uncomfortable. I wish you the best of luck with both your pregnancy and your dancing