In fact, if you have never been to a chiropractor before now is the time to start. You should be visiting one at least once a month. Some of the things a good chiropractor can do for you include improving circulation, promoting better digestion, getting rid of back and leg pain, eliminating headaches, and providing a feeling of serenity and relaxation.
The best time to start is in the second trimester when your body is really starting to change but you have gotten past your nausea of the first trimester. The sooner you start the better since chiropractic care is preventative and could solve many of your problems before they even begin.
However, as with anything else, it is best not to start seeing a chiropractor until you have spoken with your doctor.