Canadian Practical Nurse Registration Examination (CPNRE) 2025 – 400 Free Practice Questions to Pass the Exam

Naegle's Rule is a widely used method for estimating a due date based on the first day of the last menstrual period (LMP). The correct approach involves adding 7 days to the LMP and then subtracting 3 months. This calculation accounts for the average length of a conception cycle and helps determine the expected delivery date.

Understanding how this method works is essential. The reason for subtracting 3 months aligns with how pregnancy is typically calculated, which starts from the first day of the last menstrual period rather than the date of conception. By adding 7 days, you effectively adjust for the average duration of a menstrual cycle and the gestational period of approximately 40 weeks.

In the context of the other options provided, the incorrect methods do not align with the established guidelines of Naegle's Rule. For instance, adding 3 months and subtracting 7 days disrupts the typical time frame used for calculating gestation. The formula must accurately reflect the cycle and developmental stages of pregnancy to yield an appropriate estimate. Thus, the correct answer centers on the well-established formula of adding 7 days to the LMP and subtracting 3 months, making it essential for healthcare practitioners in estimating due dates for expectant mothers.