The inability to sleep at night in the fourth month of pregnancy is generally related to the secretion of hormones in the body. The increased secretion of estrogen in the body after pregnancy can affect the neurotransmitters in the brain, which can cause difficulties in falling asleep or short sleep periods. Sleep can also be affected by stress or tension after pregnancy. In the fourth month of pregnancy, the uterus enlarges, the belly bulges, and the fetus gradually increases in size, which can cause poor reflux or cause edema in both lower limbs. As the enlarged abdomen affects the sleeping posture, it leads to strain, and it is easy to have restless sleep and wake up easily during sleep, which are all physiological manifestations. You should relax and listen to soft music in moderation before going to bed to slowly relieve this symptom.