How to calculate the last menstrual period: 1. The method of calculating the last menstrual period of a friend who is assisted by artificial insemination: The date of insemination minus 14 days is the date of last menstrual period. For example, if a woman has artificial insemination on January 20, her last menstrual date is January 6. (1) If the embryo is transferred on the 3rd day, the last menstrual date is the date of transfer minus 17 days. For example, if a woman’s transfer date is January 20, her last menstrual period will be January 3. (2) If day 5 and day 6 blastocysts are transferred, the last menstrual period will be the transfer date minus 19 days. For example, if the transfer date is January 20, the last menstrual period will be January 1. Calculation of the expected date of delivery: All maternity dates are calculated by adding 9 to the month of the last menstrual period and adding 7 to the date of the last menstrual period. For example, if a woman’s last menstrual period is February 3, 2014, the maternity date will be approximately November 10, 2014.