1. Calculation method of pregnancy time The calculation method of pregnancy time is determined by the time of the last menstrual period. Usually the first day of the last menstrual period is used as the starting point of the pregnancy, and then 280 days are added to get the expected date of delivery. This time calculation works for most women, but may not be accurate for women with irregular periods or conditions such as polycystic ovary syndrome. 2. Signs and symptoms of early pregnancy In the early stages of pregnancy, many women will experience breast tenderness, nausea and vomiting, fatigue, etc.