Jane A. Foley Jane A. Foley | Sonographer | Maui, Hawaii Facebook_Icon_2013_Version_1C-scr Facebook_Icon_2013_Version_1C-scr

Jane Casper-Foley

Decoding God's Ultrasound

Author, Sonographer, Dream Expert, Speaker

“On the day of conception you are considered 2 weeks pregnant”

Dating by a first trimester ultrasound:

•So how do you find an estimation of when you conceived from ultrasound?

•The first trimester or earliest ultrasound is most accurate.


•For example: if you had your ultrasound on

                June 13th, which dated you at 6 weeks 5 days

•Subtract 2 weeks from 6 weeks 5 days = 4 weeks 5 days

•Using a standard calendar

•Conception = May 11

•You may also use the Spiral Calender  

a.The spiral calendar developed by Eve Hogan is a year at a glance.  This calendar makes it possible to tract and observe your daily activities or goals for the year with a one-page calendar.  This calendar also allows the ease of counting backwards quite easily.

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Just remember -- The most common mistake when trying to determine the day of conception is not counting all the way back to day 1! You will be two weeks off if you make this miscalculation.

Please note that with the human body there are no EXACT answers when it comes to many, many conditions. The dating of a pregnancy is an estimated date gathered from thousands of measurements taken from a cross section of women. So here we go…


When dating a pregnancy, whether it is from the last menstrual period (LMP) or an ultrasound, two extra weeks are always included in the calculation. Yes…this is the “Missing Two Weeks” and I know it is somewhat confusing.


During the first two weeks of "pregnancy" your body is preparing for pregnancy. The medical community assumes that exactly 2 weeks into your cycle, on day 14, ovulation occurs. This is when the egg pops out of the ovary and starts its travel down the fallopian tube.


Dating by last menstrual period:

To help with the explanation, I will use January 1st as the first day of your period.

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If your period was on the first of the month, on the 14th, even though this is the "day of conception," you are considered two weeks pregnant. The counting starts on the first day of your period.

The Missing Two Weeks