What is Naegele’s Rule?

If you are into parenting, you might have heard this term before: “Naegele’s Rule?”- Do you know the actual meaning of this term? We have encountered many parent-to-be women wondering about this term as they do not have any clues about Naegele’s Rule! What is Naegele’s Rule?- Let’s find out the answers!

What Is Naegele’s Rule – Overview

Naegele’s Rule is a term used to calculate the delivery date of women. If you go to nursing school, you will be taught to use Naegele’s Rule to determine the delivery date of a woman. In this guide, we will explain everything about this term.

How to Calculate the Delivery Due Date

There are two ways to calculate the delivery date of pregnant women: one by using the standard method, i.e., using the Pregnancy Wheel, and the second one is a widely used method by the professionals, i.e., the Nagele’s Rule.

What Is Naegele's Rule

What is Naegele’s Rule – How do you calculate the delivery due date?

Method 1: Calculate a Woman’s Due Date by Using the Pregnancy Wheel

Most doctors prefer to use this standard method to determine the due date of a pregnant woman. You can easily calculate the due date with access to the pregnancy wheel.

The wheel features months and dates to calculate the due date. The first thing you need to do is select the LMP from the wheel. When you choose the LMP date, the pregnancy wheel will display the due date instantly.

Yes, it is that easy! It doesn’t ask for anything else; select the LMP and determine the due date. It hardly takes a minute to calculate the due with the pregnancy wheel.

Method 2: Calculate Woman’s Due Date by Naegele’s Rule

Naegele’s Rule is a more professional way to calculate a pregnant woman’s due date, as it involves some calculations. In nursing schools, students are taught to calculate the due date using this method.

Key Points about Naegele’s Rule:

  • There are some points that you must consider before you start the calculation of your due date using Naegele’s Rule. To determine the due date for any other person, you must ask her about these points before you begin the process.
  • Using this method, the woman’s last menstrual period, i.e., LMP, is crucial to determine the due date. Without knowing the LMP, you will never calculate the due date.
  • The method calculates the due date using 28 days a month. A woman’s gestation period is 40 weeks or 280 days. This method uses the same technique to determine the woman’s due date.
  • Use 28 days of February, even if it’s a leap year. It keeps the calculation simple.

Remember that Naegele’s Rule is just for estimating a pregnant woman’s due date. You also have to follow your doctor’s guidance.

Naegele’s Rule is a more professional way to calculate a pregnant woman’s due date, as it involves some calculations. In nursing schools, students are taught to calculate the due date using this method.

The rule asks to add seven days to your LMP and then subtract three months from the same. Here’s an example to know about the due date in a better way.

Example of Calculating Due Date by Naegele’s Rule

If your LMP was December 1, then

Add seven days to the LMP date, which is December 8. Then subtract three months, leading to September 8 of the following year, not 2019 as initially stated.

Thus, for an LMP of December 1, 2019, the corrected due date calculation using Naegele’s Rule should result in September 8, 2020. Naegele’s Rule estimates the due date by adding one year, subtracting three months, and adding seven days to the LMP, reflecting a standard gestational period of approximately 40 weeks from the last menstrual period.

What if I Forget My Last Menstrual Period Date?

If you do not remember your last menstrual period date, healthcare providers have several methods to estimate your due date. These methods may include using early ultrasound data, particularly useful in the first trimester when ultrasound measurements provide the most accurate estimation of gestational age. Your healthcare provider can use measurements taken during the ultrasound to estimate the gestational age of the fetus and calculate a due date. This method is often used in conjunction with known information about menstrual cycles or ovulation dates if available, to provide the most accurate due date estimation.

Calculate the Last Menstrual Period Date

If you know the week of your last menstrual period, your doctor will determine your LMP quickly. It is easy to remember the week of your LMP, and you must know about it.

If you are completely unaware of your LMP, your doctor will determine the due date using the advanced method- ultrasound method. The ultrasound process tells you more about your due date and other things about your growing baby. Ultrasound is not required if you know your LMP.

How to Calculate the Due Date if a Woman Has Irregular Periods?

Many women have irregular periods or long cycles, making calculating a due date tricky. Thankfully, there are ways to determine the due date of these women.

Doctors prefer to use the standard pregnancy wheel method, i.e., the 28-day cycle, to calculate the due date. However, adding some calculations to this method can easily determine the due date.

They calculate the due date by using the woman’s second half cycle, i.e. 14 days. That is the time for ovulation for the next period. If your period is 36 days, then you might have ovulated on day 22.

It is a general way to determine the ovulation dates for the months. You must use the adjusted LMP to calculate the due date for long cycles and irregular periods. Once you determine the ovulation date and the LMP for that particular month, the pregnancy wheel can help.

Here’s a calculation that helps you determine the due date for long cycles or irregular periods.

If your cycle is 36 days, and the first day of your LMP was December 1, then.

  1. Add 21 days to the date i.e. December 22
  2. Subtract 14 days i.e. December 8

December 8 is your adjusted LMP. You need this to get your due date using the pregnancy wheel. Now, if you have access to the pregnancy wheel, select December 8 on the wheel and get the due date information.

The Bottom Line

In the early stages of pregnancy, the due date is determined using the pregnancy wheel. Some doctors use Naegele’s Rule to determine the same. Knowing these methods, you can help your colleagues or family members determine their due dates.

Due dates using these methods help us know the estimated delivery date. For more accurate information about the delivery, ultrasounds are prescribed by your doctor. In ultrasound, you would know about your baby’s health and growth with more accuracy!

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Current Version
March 5, 2024
Updated By
Franco Cuevas, MD

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