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

Ultrasound Ultrasound

The missing two weeks can cause a lot of problems.  I had a soldier write to me once, distraught thinking that his wife was having an affair because of the “missing two weeks.”  He was deployed and home for a short period of time.  He felt his wife’s pregnancy date did not correlate with his visit home.  


Not realizing the dating method we use in medicine, he miscalculated causing both himself and his wife much unnecessary heartache.

Calculating the exact date of conception is not an exact science.  Unless you have undergone a special procedure, like an in vitro fertilization or artificial insemination, calculating the exact date of conception is very difficult.


For a detailed explanation of the methodology used to calculate the date of conception, click here or visit the Articles page for more details.

Estimating the Conception Date

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.  

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Ultrasound Ultrasound 2016calendarsmall

Estimating the Conception Date

The Missing Two Weeks

Charting Ovulation Using The Spiral Calendar