The American Congress of Obstetricians and Gynecologists offers these suggestions to help minimize back pain during pregnancy:Other common symptoms during pregnancy that Acupuncture can help relieve are pelvic pain and back pain. Out of the twenty five percent of women who will seek medical help for these symptoms up to eight percent will be bed ridden and up to seven percent will still suffer with these symptoms after childbirth. Acupuncture has been shown to have positive results in relieving back and pelvic pain in women who are pregnant. The standard treatment for these symptoms is physical therapy Acupuncture has evidence suggesting that it may be more effective. Acupuncture allows for low risk treatment that does not involve pharmaceuticals to treat lower back pain and pelvic pain in pregnant women.

Choose shoes that offer good support in the arch and have low, but not flat, heels.
Get someone to help you when you're lifting anything heavy.
Prop up one foot on a box or low stool when you're standing for a long time.
Put a board beneath your mattress if it's soft. Make sure you don't lift the mattress by yourself.
To lift objects, squat with your knees bent and your back straight.
Use a chair that provides support for your back, or tuck a little pillow behind your lower back.
If you sleep on your side, place a pillow between your knees.
Treat yourself to a light back massage, or apply a heating pad or a cold pack to the lower back.
Ask your doctor about performing exercises to strengthen the back muscles.

Source: http://www.acog.org/