27 weeks of pregnancy is in the middle of pregnancy, the hardness of the stomach is mostly caused by physiological contractions, which is a normal pregnancy reaction, in addition, digestive system diseases may also appear this performance, but less common. 1, physiological contractions: start to appear in 12-14 weeks of pregnancy, and become more frequent in the middle and late pregnancy, characterized by sparse, asymmetric, irregular contractions, short duration and long intervals, weak intensity, the pregnant woman feels that her abdomen is tight and hard, but generally no pain and other uncomfortable symptoms. This is mostly related to the rapid development of the fetus in the middle and late stages of pregnancy and the consequent increase in the size of the uterus, which leads to the feeling of tension and hardness in the abdomen, if it is not accompanied by abdominal pain, vaginal bleeding and increased vaginal discharge, it is generally a normal pregnancy phenomenon. In addition, as the pregnancy progresses, the physiological contractions can gradually become regular and accompanied by abdominal pain near the full term, at this time, most of the contractions are caused by preterm labor, you need to seek medical attention in time for delivery; 2, preterm abortion: if you have a hard belly with abdominal pain, vaginal bleeding or abnormal discharge in the 27th week of pregnancy, you should consider the possibility of preterm abortion in the middle of pregnancy, you must seek medical attention as soon as possible for relevant examinations, after a clear diagnosis Start fetal preservation treatment as soon as possible to ensure the health of pregnant women and fetuses and prevent adverse consequences; 3. Digestive system diseases: including gastrointestinal dysfunction, irritable bowel syndrome, intestinal obstruction, acute pancreatitis, etc., mainly because of intestinal distension and hard belly, intestinal discomfort may also induce contractions, so combined digestive system diseases need to be dealt with in a timely manner.