The hard protrusions that can be felt when lying down in the fourth month of pregnancy are mostly related to the enlargement of the uterus, if there is no abdominal pain and vaginal bleeding phenomenon does not need special treatment, if there is abdominal pain and vaginal bleeding phenomenon, we should keep the fetus in time for treatment. The fourth month of pregnancy into the middle of pregnancy, the rapid development of the fetus, the gradual enlargement of the fetus will oppress the uterine wall, resulting in the uterus protruding, lying down to feel the hard protrusion of the uterus and the fetus, as long as the pregnant woman does not have abdominal pain and vaginal bleeding and other abnormal phenomena, that is, it is a normal phenomenon, pay attention to the regular pregnancy checkups can be done, do not need to do other treatments. If a pregnant woman lying on her back to feel the hard protrusion, but abdominal pain and vaginal bleeding phenomenon is abnormal, may be contractions caused by the aura of miscarriage, to go to the hospital in time to do ultrasound, give magnesium sulfate to inhibit contractions to protect the fetus treatment, and to rest in bed, forbidden to have sex and exertion. Therefore, the fourth month of pregnancy lying down can feel the hard protrusion of most of the normal, but if abdominal pain and other symptoms of discomfort should be timely examination and treatment.