Causes of pregnant women waking up in three or four include drinking too much water, back pain, sleep disorders and so on. 1. Drinking too much water: If a pregnant woman drinks too much water before going to bed, coupled with fetal development will squeeze the bladder, when the water after metabolism into the bladder, the water increases, pregnant women hold urine feeling strong, three or four pregnant women are prone to wake up to urinate. 2. Lumbar pain: pregnant women in the body of the fetus as a result of continuous growth, whether standing or lying down, easy to increase the burden on the lumbar spine. At three or four o’clock when the fetus activity is large, it is easy to push and pull the lumbar spine near the fascial muscles, lumbar strong pain and discomfort is easy to make pregnant women wake up. 3. Sleep disorders: pregnant women due to changes in the internal environment, it is easy to accompany sleep disorders. Symptoms can be seen in the difficulty of falling asleep, easy to wake up in the middle of sleep, after waking up is not easy to go back to sleep, and so on. If a pregnant woman wakes up at three or four o’clock, after changing her lifestyle habits still do not see any improvement, it is recommended to go to the hospital.