Dress in loose-fitted clothing. This will go far to alleviate discomfort and overheating. If you experience hot spells, a small fan is also a soothing solution. Empty your bladder often to alleviate discomfort and prevent urinary-tract infections. It's as important for you to maintain your professional appearance as it is for you to maintain your normal workflow.
Work is often about impressions.
If you look more professional, you'll feel more professional and will probably be perceived as more professional. Continue to dress as professionally as possible, while remaining comfortable. Wear appropriate undergarments. Looser-fitting underwear and a more supportive bra may be just the trick. Keep your maternity wardrobe simple.