Muscular or renal, severe lower back pain during pregnancy is very common. 80% of pregnant women experience it.
As your belly gets rounder, your back becomes more arched, and your abs and ligaments become more stretched. As a result, you may experience severe lower back pain, even in the buttocks. Severe lower back pain can also be a urinary tract infection, accompanied by burning in the bladder.
To reduce the risk of lower back pain, drink plenty of fluids, lie down or sit up as much as possible, limit your weight gain to 22 to 26 lbs and wear comfortable shoes.
If you have any concerns, don't hesitate to ask your doctor for advice.