Estimating Date of Conception

Question

How can my fertility doctor be sure I conceived on May 14? My period started on April 30. My six week five day ultrasound showed the baby at 7.5mm and my 7W5D ultrasound showed the baby at 14 mm. He isn’t dating my pregnancy from my LMP. How can he be sure I didn’t conceive on May 11 for example? I have had fertility problems for a long time and I don’t know how he can tell if I ovulated early or not.
Alicia

Answer

Last Updated: January 31, 2022
Dear Alicia,

Thank you for visiting our web site, and contacting us. The ultra sound measures and observes the development of your baby. Remember sperm can live up to five days in the woman’s body before ovulation. It is possible you had intercourse on May 11 but didn’t conceive until May 14. Your doctor can give you a good estimate of when you conceived based on the baby’s development. It is a more accurate way than from the LMP because the timing of ovulation can vary. If you learn a Natural Family Method of charting your daily menstrual events, you will be able to recognize the time of ovulation, the days you are fertile and the days you are infertile in each cycle. This will give you an accurate way of dating the beginning of your next pregnancy. If you keep a daily chart, your fertility problems can be diagnosed and treated more easily, as well. NFP teachers in California are listed on this web site.

Judy Wilmurt

Answered By:

Judy Wilmurt
Judy Wilmurt, Professional Member of CANFP, and past member of the Executive Board, taught the Creighton Model FertilityCare System of NFP in the Oakland region, wherre she resides with her husband Eric.

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