There are two types of pregnancy back pain. One of them is lumbar pain, a lower back pain that is located just above the waist, and might stretch out to your legs. This type of back pain can strike anyone, pregnant or not. Then, there is posterior pelvic pain, which is centered around your buttocks. Unfortunately, it is entirely possible to suffer from both types of back pain at once while you are pregnant. There are some things that you can do to avoid and cure back pain in pregnancy, but there are no real guarantees that your back won't hurt. Here are some things that you can try to get relief from back pain, or to prevent it.
1) Exercise. Believe it or not, working out makes back pain better or even prevents it a lot of the time. Swimming, yoga, or "warming up" exercises are best for your back.
2) Getting regular massages can help immensely. While I was pregnant, I got back massages twice a week, and they were just wonderful. Pregnancy can be a perfect excuse to pamper yourself!
3) Avoid carrying heavy items, or at least make sure that you carry them properly, with the right posture. When you bend to pick something up, do it from the knees and legs, and don't curl your back. The same goes for getting up again.
4) When you stand up, ensure that you are upright, and not bent. Don't stand for long periods of time if you can avoid it.
5) Wear the right shoes. Sports shoes or flats are great for pregnancy, and for proper posture. Heels are not.