If the due date is estimated from the last menstrual period, the last menstrual period is April 8, and the due date is January 15 of the following year. For women who have regular periods, you can use the last menstrual period to calculate the due date. The specific calculation method is to add 9 or subtract 3 to the month, and add 7 to the date, for example, the last menstrual period is April 8, April minus 3 is January, 8 plus 7 equals 15, which is the expected date of delivery on January 15 of the coming year. However, some women have irregular periods and it is recommended that they go to the hospital for an ultrasound in the early stages of pregnancy to project an accurate due date based on the ultrasound in the early stages of pregnancy. The due date is also relative to the time of labor, if the difference between the front and back within a week can also not be adjusted.