Early? Late? Exactly on Time? Due Date, Shmue Date

pregnancy due date

The term “due date” is a misnomer. 

Your library book has a due date, your final paper  has a due date, your status report for work has a due date.

But a baby? No such thing. The “due date”  is merely the middle date of the four week time period (38-42 weeks) during which most women give birth. I therefore prefer to refer to it as  the “40th week” date.

Tip: Did you know that for 1st births, the “due date”, can be on average a week later than for consequent births? (See Heart and Hands, by Elizabeth Davis.)

This date is often miscalculated when:

  1. You don’t know the date of the first day of your last menstrual period (LMP), or
  2. You know your LMP, BUT your menstrual cycle was not 28 days.

Why does this matter?

  1. We want to know the right window of “when to expect”. It is empowering to know that generally speaking, you will likely give birth during the 38-42 week window. With inaccurate dating, women are often disappointed, thinking their baby “should have come already” when actually, it’s perfectly normal for it to keep growing inside of you.
  2. Avoiding unnecessary inductions. Women are often pushed to unnecessary inductions based SOLELY on the date, even as early as 41 weeks. While this is a flawed policy, oftentimes this date is also miscalculated, in other words, they might be trying to induce you at an even earlier date!  Knowing this date can help you plan with your care provider.
  3. Knowing if it’s a preemie. A baby born before 36/37 weeks is considered a preemie.


I) Most Accurate of All:

    If you had an ultrasound before week 11 , you can use the estimated due date (EDD) from  the ultrasound. This is considered extremely accurate, the earlier the more accurate.  Ultrasound dating after week 11 is not reliable, as by that point it’s big enough to be too vast of a comparison – like comparing a six year old Asian with a six year old Swede – hello?
    If your menstrual cycle was usually 28 days – use First Day of Your Last Menstrual Period (LMP), and then use any “Due Date Calculator” online.

2) Pretty Darn Accurate:

    If your cycle was not 28 days, then add or subtract the number of days’ difference.  For example, if your cycle was 35 days, add 7 days to the first day of your last period (LMP), and then calculate using a Due Date Calculator.  If your cycle was 25 days, subtract 3 days from LMP, and then calculate using a Due Date Calculator .  Many due date calculators online will allow you to enter in your First Day of Last Menstrual Period (LMP)– just Google “due date calculator”.

3) So-So Accuracy:

  • Date of Positive Pregnancy Test. Generally speaking, a blood test will register positive by one week after conception, and a home pregnancy test (via urine on a stick) 2 weeks after conception.
  • “Love” Dates: If you wrote down your “love” dates, and you know when you were expecting your period, this might give you better insight. Usually, conception happens 14 days before your next period would have arrived. This will not provide you a precise date, but would likely give you the week. Remember, sperm can survive up to 5 days waiting for that egg, but the egg can survive 12-24 hours. (No comment;)

I wish all of you the most healthy pregnancy, however long or short it may be!


© Pamela Hodson | Dreamstime.com

One thought on “Early? Late? Exactly on Time? Due Date, Shmue Date

  1. Hi Chaya! I missed the event at your home last week because the woman I am too accompany was having contractions. Well, we are still here a week later and I enjoyed reading your post about “due dates!”
    May we meet at many joyous occasions!
    Kol tuv,
    Chava Dumas

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