To calculate the estimated due date (EDD) based on the first day of a woman's last menstrual period (LMP), you can follow these steps:
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Determine the LMP date: Identify the first day of the woman's last menstrual period.
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Add one year: Start by adding one year to the LMP date.
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Subtract three months: From the date obtained in step 2, subtract three months.
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Add seven days: Finally, add seven days to the date obtained in step 3.
This method is commonly referred to as Naegele's Rule and provides a rough estimate of the due date, which is typically around 280 days or 40 weeks from the first day of the last menstrual period.
Example:
- LMP Date: January 1, 2023
- Add one year: January 1, 2024
- Subtract three months: October 1, 2023
- Add seven days: October 8, 2023
In this example, the estimated due date would be October 8, 2024.
Note:
Keep in mind that this is an estimate, and actual delivery can occur anytime within a window of about two weeks before or after the due date. Additionally, other factors such as cycle length and individual health can influence the accuracy of this estimate. It is always a good idea to consult a healthcare provider for more precise dating through ultrasound or other methods.