The phenomenon of umbilical cord blood reflux during pregnancy is very dangerous, which usually causes harms such as fetal malnutrition or intrauterine hypoxia. 1. Malnutrition: Cord blood reflux will cause the fetus to lack sufficient nutrients, resulting in fetal anemia and malnutrition. 2. Intrauterine hypoxia: Cord blood reflux will lead to insufficient supply of oxygen to the fetus, resulting in intrauterine hypoxia, and in severe cases, it can even lead to fetal asphyxia, causing fetal death in the uterus, which is an undesirable outcome of pregnancy. Therefore, cord blood reflux is a very dangerous phenomenon, and pregnant women must maintain good living habits and undergo regular maternity checkups. If you find any abnormality, you should go to the hospital in time for examination and consultation, early detection and early treatment to prevent serious consequences.