It is normal to have back pain in the fourth month of pregnancy, which is caused by the increasing fetus pressing on the lumbar nerve, and can also be considered to be related to calcium deficiency as well as one’s own constitution and uterine position, as long as it is not combined with abdominal pain and vaginal bleeding. It is recommended to take more rest and stay up less, pay attention to warmth, exercise properly, eat more calcium-containing food and also take calcium tablets, strengthen nutrition and eat more protein-containing food, have a balanced diet and eat more vegetables and fruits, don’t sit too long and don’t lie down all the time, keep your mood relaxed and do regular pregnancy checks.