Using Naegele's rule, what is the estimated due date if the last menstrual period began on July 20?

Using Naegele's rule, what is the estimated due date if the last menstrual period began on July 20?

• A. March 18
• B. June 12
• C. May 7
• D. April 27

Answer: (D)

Naegele's rule estimates the due date by adjusting the last menstrual period: subtract three months, add seven days, and then add one year. If the last menstrual period began on July 20, subtracting three months gives April 20. Adding seven days yields April 27, and adding one year moves it to April 27 of the next year. So the estimated due date is April 27. The other dates don’t result from this rule because they don’t follow the month-stepback and day-addition sequence that Naegele’s rule prescribes.

Naegele's rule estimates the due date by adjusting the last menstrual period: subtract three months, add seven days, and then add one year. If the last menstrual period began on July 20, subtracting three months gives April 20. Adding seven days yields April 27, and adding one year moves it to April 27 of the next year. So the estimated due date is April 27. The other dates don’t result from this rule because they don’t follow the month-stepback and day-addition sequence that Naegele’s rule prescribes.