There are many reasons for back pain during pregnancy, which may be caused by hormonal changes, lack of calcium, fetal compression, back diseases and so on. 1. Hormonal changes: During pregnancy, under the influence of estrogen and progesterone, the pregnant woman’s body may undergo changes that are favorable to childbirth, such as ligament laxity, and so on, and the pregnant woman may experience lumbar soreness. 2. Calcium deficiency: As the fetus grows, the calcium absorbed from the mother will gradually increase. If pregnant women do not supplement calcium in time, it may lead to their own calcium deficiency and symptoms of lumbago. 3. Fetal compression: with the increase of pregnancy weeks, the fetus continues to increase in size and weight, for the pregnant woman’s lumbar compression will also increase, may produce lumbar pain performance. 4. Lumbar Disease: Pregnant women who have lumbar disease, such as lumbar muscle strain, lumbar disc herniation, etc., with the changes in the body after pregnancy, making the symptoms gradually aggravate, and lumbar pain symptoms. There may also be other causes of back pain during pregnancy, it is recommended to consult a doctor in a timely manner, improve the relevant examinations, under the guidance of a professional doctor to clarify the cause of the disease, targeted treatment.