How to Calculate Your Pregnancy Due Date/ Expected Date of Delivery?

Is your Urine HCG test positive for pregnancy? So this is high time for you to find your Expected Date of Delivery (EDD) of Pregnancy. Simply the Due Date for the Pregnancy.

As Obstetrics and Gynecology clinicians, we use a few different techniques to calculate the correct due date for a pregnancy. This calculation of the Expected Date of Delivery (EDD) can be done using manual and ultrasound-based techniques.

The calculation of due dates uses different techniques and rules in various methods. The Last Menstrual Period (LMP) based manual calculation methods of the Expected Date of delivery is mainly based on “Naegele’s Rule“. The Ultrasound method focuses on Head Circumference(HC) and a few other measurements.

How to calculate the Pregnancy Due Date/ Expected Date of Delivery using Naegele’s Formula?

What is the Naegele’s Rule?

Naegele’s Rule says, ” The Expected Date of Delivery for a baby will be on 280 days (40Weeks) following the date of the Last Menstrual Period (LMP).”

EDD = LMP + 280 days.

What is Modified Naegele’s formula?

We, as clinicians, have adopted and altered the original Naegele’s formula for easy usage. The new formula is called the Modified Naegele’s formula.

Here we use the following formulae to calculate the Expected Date of Delivery according to Naegele’s Rule.

EDD= (LMP+1year) – 3Months + 7Days

According to the Modified form of Naegele’s formula, we need to add 1 year (12 months) to your LMP, deduct 3moths and again add another 7 days.

As an example;

If your LMP is the 25th of April 2019, you need to deduct 3moths from that. That is the 25th of January. Again you need to add 7days to January 25. That is the 1st of February. Last you need to add another 1year. Finally, the EDD/ due date is the 1st of February 2020.

Accuracy of manual method of EDD using Naegele’s formula

This is a 50% accurate method. However, suppose your dates are more than 28days. In that case, you need to add an additional number of days to your Expected Date of Delivery. Or if less than 28days, you need to reduce the less no of days from your expected due date.

As example;

If you have a 35days cycle, you need to add 7 days to your Calculated Due Date. That is 7 days to 1st of February > 8th of February 2019
If you have 21 days cycle, you need to reduce 7 days from the Calculated Due Date. 7 days from the 1st of February to> the 25th of January.

Calculate the Pregnancy Due date / Expected Date of Delivery by Pregnancy Wheel

The Pregnancy Wheel is another simple way of calculating the expected delivery date.
If you know your LMP, you can direct the arrow to that date and get the result without any calculation. This is also a simple tool created by applying Naegele’s Formula. This is the most commonly used manual method for calculating the Pregnancy Due Date in clinical practice.

Online Expected Date of Delivery Calculator

You can calculate Expected Date of delivery with our Due Date Calculator Online with few minutes.

Calculation of Pregnancy Due Date with the Due Date Calculator app.

Instead of using manual techniques, most pregnancy clinicians and pregnant women are nowadays used to calculating the expected delivery date using different mobile apps. Most of the theses are freely available in the AppStore and the istore.

These pregnancy due date calculator apps use the same techniques as Naegele’s Rule.

If you visit any AppStore, hundreds of Due Date Calculating Apps exist.

• pregnancy calculator
• Due date calculating wheel
• Due Date Calculator Apps
• Due date predictor
• Due date calculator
• Pregnancy due date calculator
• EDD delivery calculator
• due date calculator

These are some of the common names used by these applications, and you might find a suitable one. Some of these mobile applications may have many advanced options like Date of conception, End of Trimesters, Timing of USS or other basic investigations, etc.

However, whether you use the manual method, wheel method or automated method with the app, you are using Naegele’s formula to calculate your EDD. But this, Naegele’s formula may have some limitations in certain circumstances.

Limitation of using Naegele’s formulae for calculating the EDD

Women with Oligomenorrhea/ Irregular periods
Women who were on Lactational Amenorrhea
Women are on some kind of birth control methods like COCP or Deport.
You may need a USS to have a proper EDD in this situation. Because you can’t have a proper LMP. In addition, when the mother is not sure about the LMP again, you need a USS-based EDD.

Finally, suppose you are a woman with a regular menstrual period and know your last menstrual period correctly. In that case, you can have EDD using any of the above methods. Unless you may need the help of USS. In addition, if you are unsure which method to use, just meet your obstetrician or midwife for clarification.

How to calculate Pregnancy due date in twins and other multiple pregnancies

Now you know Now you know many methods to calculate your expected date of delivery. Suppose you have multiple babies in your tummy. It may be twins, triplets, or quadruplets. But how do you calculate the due date for them?

How to calculate the pregnancy due date for twins, triplets, quadruplets.