Level 1: Overview of pregnancy reactions Pregnancy is an important moment in a woman\’s life, followed by a series of physical and psychological changes. These changes are called pregnancy reactions, including early pregnancy reactions, pregnancy reactions, and prepartum reactions. Let’s learn about them one by one below. Early pregnancy reactions: 1. Breast development After pregnancy, due to the increase in estrogen secretion, the breasts will gradually become firm, sensitive and slightly painful. 2. Stop of menstruation. Stop of menstruation is the most obvious sign of pregnancy.