By Idries Abdur-Rahman, M.D., FACOG
Author, Everything You Ever Wanted to Know About Pregnancy



Right after you get that positive pregnancy test, your next question is probably “when is my baby due?”. Don’t forget to check out our book Everything You Ever Wanted to Know About Pregnancy (But Were Too Afraid or Embarrassed to Ask), available in print and digital on Amazon, and be sure to download our free Everything Pregnancy-Pregnancy tracker app. Okay, shameless advertising plug is done, how exactly can you determine when your bundle of joy is going to make his or her exit?


1). Nagel’s Rule:

If you know when your last menstrual period started, the easiest way to figure out your due date is to use something called Nagel’s Rule. A pregnancy calculator like the Everything Pregnancy app can do the calculations but even if you are not mathematically inclined, you can easily use Nagel’s Rule to calculate your due date.

So, how do you do it? Well, you simply take the first day of the last menstrual period, add one year, subtract three months, and then add seven days. That’s it! Just bear in mind that while Nagel’s Rule provides a really good estimate, it is based on an “ideal” 28-day menstrual cycle, and it assumes that you ovulate on day 14. This is not necessarily the case for many women.

Want to figure out your due date? Head on over to the Everything Pregnancy app and check out the Nagel’s Rule feature. You can also follow your pregnancy week by week there.


2). Ultrasound:

Now, what happens if you have irregular periods or you just don’t know when your last period started? In this case, your doctor or midwife will probably order an ultrasound. The earlier you get the ultrasound, the better in terms of accuracy. Just remember though, ultrasound is not perfect and the final due date will ultimately be determined by your doctor or midwife.

Do you have a question for the docs? Head over to the Everything Pregnancy website to submit your questions!


Everything you’ve read are just our recommendations and they do not constitute medical advice. Be sure to speak with your doctor or midwife before making any medical decisions.


If you want more where this came from, the book is available in both print and digital formats from Amazon RIGHT HERE

You can also get the free Everything Pregnancy app in the GOOGLE PLAY STORE and APPLE I-TUNES.


If you have any pregnancy-related questions, submit them on our website

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About The Docs


Idris is the creation of twin OB/Gyn Doctors Jamil and Idries Abdur-Rahman. Jamil (Dr. J) and Idries (Dr. I) were inspired to start after participating on season 22 of CBS’ ‘The Amazing Race’.

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Everything You Ever Wanted to
Know About Pregnancy:

But Were Too
Embarrassed or Afraid to Ask

by Idries Abdur-Rahman (Goodreads Author),
Jamil Abdur-Rahman MD, Nikia Bilal (Editor)

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