An introduction to early pregnancy reactions: All the details you need to know Early pregnancy reactions refer to a series of physical and emotional changes that occur in women after pregnancy, and are an important manifestation of pregnancy. Below, we will introduce the details of early pregnancy reactions in four aspects. 1. Time and symptoms of early pregnancy reactions Early pregnancy reactions usually start around the 4th week after pregnancy. Symptoms are not present in all women, and the degree of symptoms also varies from person to person. However, common early pregnancy reactions include: 1. Breast swelling and pain: breast It will become sensitive, sore, and swollen. 2. Nausea and vomiting: Many pregnant women experience nausea, vomiting or nausea in the morning or after meals.