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When Did I Conceive?

by Katlyn Joy | May 12, 2011 12:00 AM
51 Comments


While actual dates of conception are difficult to determine because of the number of biological unknowns, it generally is fodder for conversation or guesstimating. However, it's fun to try to find out if it happened that long weekend in the mountains or when you made up after that silly fight you had over cleaning out the garage.

Conception Math

  1. Take the date of your last menstrual period. You count this as the first day of your last period, by the way.
  2. Add 12 days to this date as this is an average range of when ovulation would occur in the typical menstrual cycle.
  3. Add another 10 days to this date and highlight those 10 days. Which of those days were you and your sweetie getting busy? If only one time in that stretch did you have intercourse, you have found your likely conception date.

Those who practice fertility charting and chart their temperatures have been seriously working at getting pregnant probably know when they most likely ovulated during their cycle by looking at the records of basal body temps and observations of their cervical mucus. Women who have predictable cycles have an even better likelihood of knowing when they actually got pregnant. Additionally, those who chart usually also keep track of the dates they had sex.

Factors that Throw Off the Calculations

Women who recently stopped taking birth control pills or used hormonal methods for birth control may not have resumed a regular cycle yet and will have difficulty pinpointing the time of ovulation. Also, those who don't have regular periods or are not the best record-keepers of when cycles occur will be at a definite disadvantage than other expectant mothers when trying to determine when baby was made.

Sperm Facts

Of course, while the egg is the focus of attention here, let's not forget that crucial ingredient to baby-making; sperm! Sperm can throw off calculations by virtue of the simple fact that they don't live just a day in many cases. Indeed, sperm can often survive a day or two, and may live up to five days. So while you may have had sex only one time in the week you conceived you may not have gotten pregnant the day you had sex. It may have occurred a couple days later.

Couples who have more sexual activity together may have a more difficult time determining the day of conception. If they only had sex once that month, well it doesn't take a special formula to determine the special time. However, couples that are more amorous have more possibilities to consider.

Hard Facts

Even with a completed chart of temps, mucus observations, dates of when sex occurred, and the last menstrual period it can be impossible to pinpoint the exact moment of conception.

Early ultrasounds coupled with the firm date of the last period however can nail down a fairly precise due date, and a corresponding likely date of conception. However, the technology is less precise as the pregnancy progresses and a baby who grows at a different than typical pace can throw off results as well.

If you and your partner are beginning the baby-making adventure and you want to know when you achieved your goal, keep careful records of your periods and keep a sex calendar as well. Consider an ovulation predictor test as well to help with more exact date. There are plenty of online due date calculators, which in reverse determine your date of conception, as well. Plus, consider some storyteller liberties when talking of that special night when you two became a family.

Implantation Calculator - Find out when implantation occurred

Ovulation Calculator - Find out when you ovulated

How is Pregnancy Due Date Calculated?


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Comments


Showing 1 - 10 out of 45 Comments
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van Apr 10, 2015 08:07:38 PM ET

My last menstrual period was around feb. 24th or 27th. when did i conceive?

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chereese Mar 31, 2015 08:14:03 PM ET

Due date is 09-25-15. when did i conceive? my due date is between 9-20-15 and 9-28-15.

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Guest Mar 29, 2015 11:56:19 PM ET

I had sex on dec 28th and 29th. please tell me, when is my due date?

Guest Apr 6, 2015 12:18:28 AM ET

I conceived on the 29th, so september 21st most likely. :)

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MIMI Mar 21, 2015 02:33:03 PM ET

My due date is august 13, 2015. when did i get pregnant?

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Nay Mar 19, 2015 10:21:52 PM ET

When did i conceive if my baby was born on 2/27/14??

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Guest Mar 6, 2015 07:53:01 PM ET

Have you found out your due date yet nina??

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xjavier Feb 27, 2015 12:17:19 AM ET

I had sex on sept 10 2015 and i'm twenty five weeks. i thought it would be twenty four weeks?

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nina Jan 22, 2015 11:34:15 AM ET

I had sex on november 24, 2014. when is my due date? help me figure this out please.

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kim Jan 14, 2015 07:55:47 PM ET

I had my son on nov 11, 2014. can anyone help me find out around what day and month i got pregnant? my last period started feb 8th, and lasted until feb 13, 2014.

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Diana Dec 29, 2014 11:04:28 PM ET

My due date is may 25, 2015. when do you think i conceived?

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