Level 1: What are the signs and reactions in early pregnancy 1.1 After menstruation is delayed or pregnancy is stopped, the levels of estrogen and progesterone in women\’s bodies will change, leading to changes in the menstrual cycle, or even delays or stops. If you have been having regular menstrual cycles and this happens suddenly, you may be pregnant. 1.2 Breast swelling and pain in early pregnancy. Due to changes in hormonal secretion, women