Symptoms such as nausea and vomiting are the most common type of early pregnancy reaction in early pregnancy. The degree of nausea and vomiting varies greatly from person to person. Generally, nausea and other early pregnancy reactions appear after 6 weeks of pregnancy. During the first month of pregnancy, the level of progesterone in the pregnant woman’s body is low because the embryo has just developed, therefore, fewer pregnant women have early pregnancy reactions such as nausea during this stage. However, there are exceptions. A small number of pregnant women can also experience nausea and vomiting during the first month of pregnancy. In these cases, the early onset and severity of early pregnancy reactions may require rehydration treatment at the local hospital if necessary. In addition, pregnant women should pay attention to the detection of digestive system diseases because some patients with gastric cancer in pregnancy have severe nausea and vomiting that last throughout pregnancy and the puerperium. Other diseases of the digestive system such as gastric ulcer can also manifest as nausea and vomiting. Therefore, if the nausea and vomiting symptoms are severe and last for a long time, patients are advised to consult a gastroenterologist to exclude digestive system diseases. In summary, some pregnant women can experience nausea in less than one month of pregnancy, which is usually mild. If the digestive symptoms are obvious and persist for a long time and do not ease as the pregnancy progresses, they should be treated as early pregnancy reactions after excluding digestive system diseases.