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How accurate is your pregnancy due date?

How accurate is your pregnancy due date?
Pregnant mother over 40 weeks and past her due date trying to patiently wait for baby

Did you know that your pregnancy due date is an ESTIMATE only?

It’s not an eviction notice, it’s not a deadline, and it’s very likely to NOT be the date that you actually give birth. 

Now, I’m not suggesting your estimated due date isn’t an important date. It’s VERY significant. It allows your provider to accurately track your baby’s development, gives insight into your little one’s growth, and it allows you to plan for approximately when Bub might make their grand entrance.

How is the estimated due date calculated?

Your baby’s estimated due date is typically calculated early on in your pregnancy. It is around 40 weeks from the first day of your last period (LMP). Your provider will probably work this out for you. Or you could try an online calculator tool.

A due date calculated based off LMP isn’t always accurate though. Especially if you have long or irregular cycles. If this is the case, your provider may refer you for a dating scan. 

A dating scan is an ultrasound done in the first 12 weeks of your pregnancy. The purpose of a dating scan is to establish how far along you are in your pregnancy. In early pregnancy, babies around the same gestational age typically have very similar measurements. So an ultrasound done at this time is able to help give a more accurate estimated due date than the date of your last menstrual period alone.

So, will my baby be born on their due date?

Only around 5% of mothers give birth on their estimated due date. That’s kind of wild, right?

Most babies will arrive anywhere between 37-41 weeks – so anywhere over the course of around a month! So, while you’ll be keeping that date in mind, try to not fixate on it too much. It’s hard, I know! Especially when you’re late in your third trimester, you’re tired and just eager to finally hold your precious baby in your arms.

But baby will come when they are ready and until then, you are doing an incredible job, Mama!

PS. It isn’t too late mamas… Our FREE Prenatal class is still available! 8 out of 10 mothers say they wish they took this before birth to ease their stress and worries. You can even watch it at your own pace from the comforts of your own home! Sign up NOW!

It’s important to note that pregnancy should be discussed with a healthcare provider to ensure safety and suitability for individual circumstances. This blog is general education only. For any personal based advice regarding you or your baby please seek advice from your own healthcare professional.


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  2. [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. Pregnancy and birth: When your baby’s due date has passed. 2008 Sep 24 [Updated 2018 Mar 22]. Available from:
  3. Morgan JA, Cooper DB. Pregnancy Dating. [Updated 2022 Sep 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:
  4. When pregnancy goes past your due date. (November 2021). ACOG.