ultrasound

[ATL7554]

My wife and I had our first ultrasound yesterday. We know the exact days of the month we had sex. the first day of her last period was 10-27, we had sex the 11th, 13th , and 15th of Nov, none after that for the entire month. So we figured yesterday when the Ultrasound was done that we were around 7 weeks. When the Ultrasound tech made the measurements, she found a clear heartbeat, it was 119, but the measurements she said only meausred up to be 5 weeks not 7. I know two weeks is a big deal, does this mean my wife cheated on me and that I'm not the dad? Doe it mean something could be wrong with the baby? We know the exact dates we had sex. Please help, veryconfused.

[Elaine Brown, MD]

Hi!
Doctors and ultrasound machines both use the period date instead of the conception date when they calculate the due date.  This is simply because as you yourself noted above there could have been at least 3 different dates for conception, or several in between.  So, the due date calculated by using the LMP always is two weeks different than everyone who uses the conception date thinks it should be.
Women who are trying to get pregnant with a man are usually pretty happy with that particular guy and are not likely to be playing around.  Women are very different from (some) men in that way.  
One other thing to consider is the built in error in the ultrasound--it is always given in plus or minus 3-4 days.
Finally, if you two were my patients, I would re-ultrasound in two weeks to check on the development, and (hopefully) put your mind at ease!
Congratulations!
Dr B

[amanda_panda1118]

hope you dont get mad that i did some research for you but this should actually put you at ease a little bit....i went to a site and entered your wifes period date and got that her due date should be august 3 of next year, which puts her at 8wks. i went to another site and used her due date to find out the conception date and they are thursday nov 5 and wednesday nov 11. not a profesional but i dont think she cheated, depending on her size and health the baby could just be small. dont worry, if you have good doctors they will find out the problem and im sure it will all turn out for the best!

the two websites i went to are, for due date www.parenthood.com/pregnancy_due_date_result.php

and for conception
http://babymed.com/Tools/pregnancy/conception_date/Default.aspx


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