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Ask Dr. C. Your Own Question
Dr. C.
Dr. C., Board Certified
Category: Medical
Satisfied Customers: 3064
Experience:  Physician with 30 years experience
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As I stated yesterday I was concerned as to the paternity of

Customer Question

As I stated yesterday I was concerned as to the paternity of my girlfriends unborn child.
We went for our first ultrasound scan today and was given a due date of 16th September.
As I stated yesterday. We had sex for the very first time on 13th January 2013 and now her due date is 16th September. This just isnt adding up.
What is your opinion?
Submitted: 4 years ago.
Category: Medical
Expert:  Dr. C. replied 4 years ago.

Dr. C. :

Hi and welcome to the site. My name is Dr. C. and I'll be providing medical information for you today.

Dr. C. :

I agree that the dating doesn't seem quite right.

Dr. C. :

The error on an ultrasound done at 13 weeks is about 7 days either direction. That would put the latest day of conception at about December 29th.

Dr. C. :

It would be better if there was a second ultrasound done EARLIER. The later an ultrasound is done, the less accurate they become. Ultrasounds done at between 6-12 weeks of gestational age have an error of about 4 days in either direction. This ultrasound is at 13 weeks gestational age so the error is slightly wider. Still, I agree that this doesn't add up.

Dr. C. :

Please REPLY if I can clarify anything else.