How do you know how many days you're pregnant?

Pregnancy time or gestational weeks, can be calculated through the last menstrual time. That is, the first day of the last menstrual period plus the late time, then 7 days for a cycle, so you can calculate how many weeks. This is a case for women with regular menstruation. So for women with regular menstruation, it is recommended to go to the hospital for a detailed examination, so that you can check to know the specific time. For the time of pregnancy and due date is a rough estimate of the time, basically can not be accurate.