Back pain is almost always benign, especially if not associated with vaginal bleeding or symptoms of a urinary tract infection (UTI). It is usually caused by a shift in weight and pressure of a growing baby on your body. The best way to relieve the strain is changing your positioning throughout the day to relieve this pressure, cold/heat therapy, and often maternity support belts later in pregnancy. If the pain is accompanied by other symptoms such as fever, chills, headaches you should speak with your doctor to make sure it isn’t a more serious condition.