Leg cramps in the fifth month of pregnancy may be caused by physiological factors, calcium deficiency, lumbar disc herniation and other reasons. 1. Physiological factors: pregnant women in their fifth month of pregnancy due to increased weight-bearing, excessive activity and long-term standing easily lead to leg muscle fatigue, excessive fatigue easily lead to leg cramps. 2. Calcium deficiency: the rapid growth of the fetus in the fifth month of pregnancy, the need for calcium increases, pregnant women do not supplement calcium in a timely manner can lead to calcium deficiency, calcium deficiency will lead to increased neuromuscular excitability, resulting in leg cramps. 3. Lumbar disc herniation: the lumbosacral area of the pregnant woman’s stress increases, it is easy to occur lumbar disc herniation, lumbar disc herniation compression of the sciatic nerve can cause motor and sensory dysfunction of the legs, which can cause leg cramps. Pregnant women with leg cramps in the fifth month of pregnancy should go to the hospital in a timely manner to improve the examination, to clarify the cause of the disease, according to the cause of the targeted treatment and treatment.