How To Calculate Your Pregnancy Due Date

Nothing is more exciting than when you finally see those double lines on the take home pregnancy test! While your mind starts swimming with who you’re going to tell first, wondering where the baby will sleep, what you will name it and of course, all of the things you’ll need before, during and after baby’s arrival, one thing is indisputable – your curiosity over how to calculate your pregnancy due date! While your doctor (and the internet!) can help you answer this question, keep on reading for some ideas on how to calculate your due date!

How do you calculate your expected due date?

If you’re curious how do you calculate due date there are several methods that can be found online on how to calculate pregnancy date. To give yourself an estimate, try the following:

  1. Note the first day of your last menstrual period (LMP)
  2. Count back 3 calendar months from that date – so if your LMP was on October 1st, three months prior would be July 1st
  3. Lastly, add 1 year plus 7 days to that date. Given the example above, your estimated due date (EDD) would be July 8th of the following year

How is EDD calculated from LMP?

To to calculate your EDD in pregnancy, see the example above. It starts with the first day of your last period. You can also calculate 40 weeks and/or 9 months forward to give you an idea of your expected due date as well.

Why do doctors add 2 weeks to pregnancy?

This is where things get a little confusing. The reason doctors tend to add two weeks to pregnancy due date is because technically, by the time most women realize that they're pregnant, it’s been around 4 weeks since their last period which is when the gestational period starts – the first day of the last period. 

Can you calculate conception date?

What’s interesting about predicting due date in pregnancy is that if the parents-to-be got pregnant the old-fashioned way, it’s easier to predict the due date based on the LMP. Conception typically occurs about 11-21 days after the first day of the last period.

However, in circumstances where pregnancy happened because of artificial insemination or invitro fertilization, conception date is fairly easy to determine as the exact date of conception likely involved a visit with your doctor.

Is ultrasound due date more accurate than LMP?

Experts suggest that ultrasounds are more accurate in predicting your pregnancy due date but only when done during the first trimester, or early into the second trimester, no later than around 20 weeks. The margin of error on ultrasounds in predicting due dates increases by a few weeks the later the ultrasound is done, otherwise, they give a fairly accurate due date.

Which week of pregnancy does delivery become safe?

It’s important to remember that every pregnancy affects women differently, even when the same woman has more than one child. That said, according to,

the risk for neonatal complications is lowest in uncomplicated pregnancies delivered between 39 and 41 weeks. The earlier your baby is born, the greater the risks to their health and survival. If born before week 37, your baby is considered a “preterm” or “premature” baby. If born before week 28, your baby is considered “extremely premature.”

What should you expect at 33 weeks pregnant?

A lot is happening in your 33rd week of pregnancy! You’re in the middle of your third trimester and your baby is as large as a butternut squash! According to What To Expect, Week by Week, at 33 weeks your baby has reached the length he'll measure at birth, but he's still busy putting on about half a pound a week. Baby’s kicks may feel sharper, you may be feeling out of breath more often, and baby’s little immune system is developing – exciting times!

What are the do's and don'ts in the 9th month of pregnancy?

While the internet is full of information on the do’s and don’t’s of your 9th month of pregnancy, the truth is you should really only be taking advice from your doctor. Depending on how your pregnancy has been, you’ll know your limitations as well as what works for you and your growing belly! Of course, try not to stress or worry – easier said than done, we know! Be kind to yourself, enjoy the time alone and/or with your partner before the new addition to your family arrives. Get your sleep, your vitamins, your gentle exercise, and prepare for your world to be changed in amazing ways!

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