How many days after pregnancy do women start to experience reactions? Pregnancy is a life journey that every woman faces. When a woman becomes pregnant, her body undergoes many changes, with varying degrees of response. This article will start from the first reaction and explain in detail how many days after pregnancy women start to have reactions from multiple perspectives, including physical and psychological. Reactions caused by physiological changes After a woman becomes pregnant, she will usually feel physiological changes within two weeks of pregnancy. These changes can be early signals of pregnancy. Some common reactions include headache, low back pain, breast tenderness, constipation, nausea, drowsiness, changes in appetite, etc.