Find Out Conception Date by Due Date & Ultrasound


Is it possible to find out conception date by due date? How can I calculate the conception date using the due date? Learn more on determining the conception date from due date, and how well to calculate it.

One of the most difficult things about conception is finding the exact day the sperm fertilized your egg to make the baby boy or girl growing inside you. You may have taken the pregnancy test, which turned out positive, but the curiosity is getting the better of you. You want to know, which day exactly your baby was conceived. Was it on that weekend getaway in summer or was it when you both visited your parents for Thanksgiving dinner?

Find Out Conception Date by Due Date Using Ultrasound
Find Out Conception Date by Due Date Using Ultrasound

It is not ridiculous to want to know when, as being a mother calls for knowing all the intricate details about motherhood, right from conception to when you finally release that child to be independent at the age of 18. The good thing is that your obstetrician gave you a due date. With that little information you can find out conception date based on due date. Let us see just how you can do that in this article.

What Are Conception Dates and Due Dates?

Before we embark on finding the conception date, it is important to understand what conception dates and due dates are. Conception date is the actual day your egg was fertilized by a strong sperm. This is because out of the millions sperms ejaculated by your partner only one swimmer gets to fertilize the ovum. Once the fertilization takes place, the egg develops into a blastocyst, which has to implant on the uterus. It takes about 7-14 days for you to affirm that you are pregnant using a pregnancy test.

The due dates on the other hand, indicate the expected day of delivery. Since, the exact day of conception is also an estimate. The due date is also estimation. Normally you can deliver your baby two weeks before the provided due date or two weeks later.

How to Determine Conception Date from Due Date

I told you can determine conception date from due date, right? How to determine conception date from due date takes a few calculations that even an 8 year old can manage, though with difficulty. You just need to add and subtract some numbers and you have your results. It is that simple.

Conception Date Based on Due Date

In order to get the conception date based on due date you will need:

  • The due date provided by your healthcare provider
  • To know your menstrual cycle
  • To know the first day of your last menstrual cycle
  • A calculator
  • A calendar, the Gregorian kind

The gestation period of a pregnancy is supposed to be 40 weeks, 10 months or 280 days if you prefer. What this means is that, there is already an allowance of about two weeks added to the period to cater for when conception could have taken place. As a result, when you come to finding the conception date based on due date, you will have to subtract first the 14 days (2 weeks) in order to get 266 days.

Now using the due date reverse from it on the calendar for 266 days. This should give you an estimated date of when you conceived.

Alternatively, using your first day of your final menses, add 14 days. You should only add 14 if you have a menstrual cycle of 28 days. If you have a longer cycle of say 30 days, you should add 16 days, and a shorter cycle of 24 days, you should add just 10 days.

Once you have added the ideal figure, it should give you the estimate of the day you conceived. Now, you will need to confirm whether this is correct using your due date. Therefore, whatever figures you obtain add 266 days to it to see if leads you to the due date provided by your healthcare provider.

If it surely does, then you have a definite conception date based on due date. In the first instance, you were reversing from the due date to obtain the conception date. In the second circumstance, you are working with your due date and first day of last menses to test if, that date is correct.

Instead of adding and subtracting, you can actually count the days on the Gregorian calendar. Using the due date, just flip through the pages of the calendar counting until you are done with 266 days backwards. It is laborious, but since you want to kill the curiosity, it is the only sure way.

In fact, by doing this, you may discover that was the actual day you had an intimate dinner with your lover and maybe you have circled the date and because you were ovulating or were five days away from ovulating, conception occurred then or on the following day.

Find Out Conception Date by Due Date
Find Out Conception Date by Due Date

Find Out Conception Date by Due Date Using Ultrasound  

In your first trimester, you should be able to get your due date using an ultrasound. Sonographers use a dating method known as crown rump. This method is accurate during this stage as later the development of the fetus may interfere with the results. Normally, the sonographer will give you an exact due date. Use that date and reverse backwards on the calendar for 266 days to get the exact day you conceived.

Going for an ultrasound in your second or third trimester may not give you an accurate due date which you need to find out conception date. You may also not know the sex of the baby you are carrying in the first trimester ultrasound.

Calculate Conception Date From Due Date

In order to calculate conception date by due date, you will need to have tested positive for pregnancy with a certified obstetrician. He or she will give you a due date based on the information you provide. The most important include your first day after your last menstrual cycle and whether you menses follow a regular or irregular cycle. This information will help the healthcare provider to come up with an expected delivery date, which you can use to calculate conception date by due date.

More on Conception:

Read More on Pregnancy Signs and Ovulation.