If you are still in your first trimester and are queasy/extremely tired/etc, etc. then I hate to tell you this but you will not enjoy Vegas. At least the noisy, action-packed Strip part. There are so many fast-moving people, smells, smoke, alcohol, partying kids all around that it might just be more irritating than anything.
If that's the case then I'd advise staying on a property that is off-Strip, such Alexic Park or Jockey Club, which offer more apartment-like villas versus a hotel casino.
On the other hand, if you are past that phase where you aren't so queasy and tired, you can still enjoy it. A pregnant woman loves good meals, and you can find delicious food in almost every variety there. Lots to do other than drinking and gambling too - the shark excursion at Mandalay Bay, the lions at Mirage or MGM, the 3D movies at Luxor, the Titanic Expedition at Tropicana, etc. And remember all the millions of choices of shows too!
Let us know how it goes.