For women with normal menstrual cycles, the due date is calculated on the first day of the last menstrual period, the month plus 9 or minus 3, and the date plus 7. The due date is approximately equivalent to 40 weeks of pregnancy, but the fetus is full-term at 37 weeks of pregnancy, which means that all organs and organs of the fetus are basically developed and perfect, and the fetus can obtain a relatively high survival capacity at this time. But not a full-term child will be born immediately, generally speaking, “ripe”, the fetus in full term in the womb can continue to develop for a period of time, the baby will grow more plump, mature and then launched to earth.