In medical terms, the gestational week in a natural pregnancy is calculated from the first day of the last menstrual period and pushed back about 280 days (40 weeks) to the expected date of delivery. For IVF pregnancies, the last menstrual period will be 14 days before the day of egg collection. The month of the last menstrual period plus 9 or minus 3 will be the month of the expected delivery, and the date of the last menstrual period plus 7 will be the day of the expected delivery. For mothers-to-be with artificial insemination pregnancies, the gestational week and due date are calculated based on the normal time of the last menstrual period. For example, if the egg collection date is March 30, 2017, and the egg collection date is pushed forward 14 days as the last menstrual time, March 30, 2017 is pushed forward 2 weeks to March 16, 2017, therefore the last menstrual time is counted as March 16, 2017. The gestational week is counted from March 16, 2017 to March 30, 2017 which is 2 weeks of pregnancy and so on. Using March 16, 2017 as the time of last menstruation, project the expected date of delivery, month plus 9 or minus 3, in this example it should be plus 9, (why? Minus 3 try to know), so the expected month of delivery is 3 + 9 = December, the date plus 7, so the expected date of delivery is 16 + 7 = 23 days. The month and date together means that the due date is December 23, 2017. As another example, if the egg collection date is September 3, 2017, the last menstrual period will be August 20, 2017 (2 weeks before September 3, 2017), then the due date will be May 27, 2018 (month 5=8-3, date 27=20+7, May 27 is of course May 27, 2018). It is important to note that the IVF estimate is only an approximate time, only about 50% of pregnant mothers will deliver on the day of their due date, it is normal to deliver 2 weeks earlier or later than the due date. Clinically, a full-term baby is a fetus that is 37-42 weeks of gestational age, and about 80-90% of pregnant mothers deliver within this time frame.