Ultrasound ET
June 7, 2013 | 20,00 EUR | answered by Dr. med. Ralf Berg
Good day,
According to my last period, the due date is 9.7.2013. This means that ovulation had taken place on 16/17.10.2012.
This due date was confirmed by an ultrasound in the 11th week of pregnancy.
Is it correct to assume that fertilization could not have occurred on 21.10.2012, as otherwise the ultrasound would have predicted a due date of 14.7.2013? I just want to know if based on the ultrasound calculation (EDD 9.7.13), ovulation or fertilization on 21.10. can be ruled out?
What are the error rates for these ultrasound calculations?
Hello
and good evening.
Unfortunately, I have to disappoint you. The error rates of ultrasound may not vary by several weeks, but +- 4-6 days is already the inaccuracy. Theoretically, the 21st of October could still be considered if your ovulation time in the previous cycle had shifted by 4 days and if intercourse had also taken place.
However, if you have a very consistent period length with low variance (+- 1-2 days) and if the due date actually occurs as calculated, it is extremely unlikely that fertilization occurred on the 21st of October if ovulation and intercourse had already taken place around the 16th/17th.
It is definitely not ruled out as per your question, if intercourse did indeed occur on the 21st of October.
I hope I was able to answer your question. If you have any further questions, I am happy to provide information.
With best regards, Dr. R. Berg
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