Naegele Rule: how to calculate the probable date of delivery

One of the first things we do when we discover that we are pregnant is calculate when our baby will be born, according to our last rule. The doctor or midwife will confirm the date on our first visit, although really only ten percent of women give birth on their probable date of delivery.

The calculation made by the doctor is based on the Naegele Rule, and today we want to explain in a simple way what it is and how you can do it yourself.

How long is a pregnancy?

Before you can calculate the due date it is important know how long exactly a pregnancy lasts. We all know that gestation lasts nine full months, but how many days or weeks exactly?

The Average pregnancy duration is 280 days or 40 weeks, although it is considered that the pregnancy has come to an end as of week 37 (259 days). If the woman arrives at week 40 and has not yet gone into labor, it could be expected until week 42 to induce it, thus giving more time for the delivery to be triggered naturally.

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What is the Nagele rule?

You can find out your probable delivery date yourself by applying the Nagele Rule, named for the German gynecologist who started using it, based on the calculations of pregnancy duration just discussed.

It consists of subtracting three months from the first day of your last menstrual period, and then adding seven days. The result is your probable due date.

Let's give an example: If the date of your last period was March 1, after three months we will go to December 1. Then we add seven days and get on December 8, which will be your probable due date.

Here you have a calendar for months and days to calculate the probable date of delivery.

In Babies and more, what are your fertile days?

Although this is undoubtedly a good estimate to calculate the probable date of delivery, it should be borne in mind that the Nagele Rule is based on regular 28-day cycles, in which fertilization has occurred in the middle of the cycle, that is, two weeks after the date of the last period.

Therefore, in the case of irregular periods or when fertilization takes place before or after the 14th day of the cycle, the date may vary.

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Video: Naegele's Rule Example with Practice Questions for Maternity Nursing NCLEX Review Nagele's Rule (April 2024).