Everything in woman hath a solution. It is called pregnancy. -Friedrich Nietzche

From The International Chiropractors Association, by Dr. Len Schwartz:

The following are a list of guidelines that the International Chiropractors Association has recommend to minimize low back strain during pregnancy:

Avoid prolonged sitting, especially with your legs crossed. Sit in chairs with proper low back support.

Try to avoid any lifting and twisting, especially at the same time. Try to think about your movements so as to avoid fast jerking motions.

Sleep on your side with your knees bent. Place a pillow between your knees to help the ligaments and muscles relax.

Follow a moderate exercise program recommended by your chiropractor or medical doctor. Try to exercise three times each week to keep your muscles strong and supportive. This will also help you with the labor and birth process.

If you are pregnant and would like to minimize or even possibly eliminate your low back pain, consult a chiropractor who treats a lot of pregnant women.