The hardness and tightness of a pregnant woman’s stomach at 28 weeks may be caused by physiological reasons, preterm labor, acute gastroenteritis and other reasons. 1. Physiological reasons: with the increase of pregnancy weeks and the enlargement of the uterus, the sensitivity of the uterus will also increase, occasionally irregular and painless uterine contractions, manifested as a hard and tight stomach, and is not accompanied by the shortening of the cervical canal and dilatation of the uterine opening and other changes, can return to normal after appropriate rest. 2. Preterm labor: regular or irregular contractions, manifested by a hard and tight stomach, often accompanied by a small amount of vaginal bleeding or bloody discharge, and accompanied by progressive shortening of the cervical canal, which can be diagnosed by combining with clinical manifestations and ultrasound examination. 3. Acute gastroenteritis: due to cause abdominal pain, diarrhea and other symptoms, can trigger contractions, manifested as a hard and tight stomach, most have unclean diet or improper diet history, combined with the history and clinical manifestations can help diagnosis. Pregnant women need to go to the hospital when their stomachs are hard and tight at 28 weeks in order to identify the cause and deal with it actively.