Monthly back and leg pain is common for the following reasons: First, lumbar disc herniation, body weight gradually increased during pregnancy, lumbar intervertebral disc load, easy to lumbar fibrous ring rupture, nucleus pulposus protrudes into the vertebral canal, compression of the spinal cord nerves, can cause lumbar and leg pain during the month of the symptoms, clinical manifestations of lumbar pain accompanied by lower extremity radiating pain, often recurring episodes of coughing, defecation and so on to make the abdominal pressure, can make the symptoms worse, bed rest pain symptoms relief. When coughing and defecation increase the abdominal pressure, it can make the symptoms aggravated, and the pain symptoms are relieved by bed rest, and the examination found that the lumbar spine forward flexion and straight leg elevation are limited, and the lumbar intervertebral disc CT and magnetic resonance examination can show the lumbar intervertebral disc herniation segment and the degree of nerve pressure. Second, lumbar muscle strain, long-term overweight can make the lumbar muscle strain, manifested as localized pain symptoms, and when serious, can cause leg discomfort.