Level 1: How long after pregnancy does the reaction begin? How long after pregnancy does the reaction begin? This is one of the biggest concerns of many expectant mothers. The truth is, everyone’s body is different, so everyone’s reaction time will be different as well. Generally speaking, early pregnancy reactions such as fatigue, nausea, vomiting, changes in appetite, etc. will occur around 2-8 weeks into pregnancy. Level 2: How long will early pregnancy reactions last? The duration of early pregnancy symptoms varies from person to person. Some people only experience mild symptoms early in pregnancy, while others may have symptoms throughout their pregnancy. Most women will feel significantly better around 12 weeks pregnant, but some women may