This is very tricky. Back pain in pregnancy has more to do with the shifting and spreading of anatomic structures and the weight of the abdominal contents as the growing fetus and fluids push forward. Then there is the issue of physicians clearance to exercise. Any exercise that you might find should be pre-cleared with the OB/GYN prior to use. Any woman that was not exercising prior to becoming pregnant should also make sure that her doctor knows this before getting clearance. I wish more women considering having children would begin an exericse program prior to attempting conception. Many doctors that I know, will not give clearance to exercise if the mother didn’t begin to exercise at least as soon as they found out they were pregnant. So get clearance. Now with that said. I have found that if aquatic exercise has been cleared. This is the best exercise for pregnant women. Clearance should be obtained specifically for water based exercise. And the doctor should be asked when the water exercise should be discontinued, either for a cause like discomfort or for a timeline discontinuation for the course of the pregnancy. Most doctors have asked my pregnant clients to stop anywhere from the start of the last trimester to four weeks prior to their due date. Exercises should become more conservative as the pregnancy progresses. My experience has been that just being in the water for a while has helped with things like back pain. Which is just as likely due the relief from gravity as it is to the exercises performed.