Need help finding out conception date

[aria1234]

Hello, i dont know who the dad is, I have been with my boyfriend for awhile and made a mistake one night. I had sex September 27th and October 4th/5th, my LMP was either the 17th,18th, or 19th of september but i remember it only last 2 or 3 days and was very light. I had an ultrasound at 8 weeks 4 days that put me at the due date of june 22nd, that means conception was the 29th of september so it points to the 27th date. Could conception still have been October 5th or after?

[AnnieBrooke]

Your question was, could conception have been October 5.  Yes, it could. There is a margin for error when using an ultrasound done in the 8th week to try to determine when someone conceived.  Because it exists, and because your dates are so close together, a DNA test seems pretty much a necessity if you want to be 100 percent certain.  That all said, it sounds like you got pregnant from the sex on the 27th.  But it is important enough of an issue that you should attempt to be certain, for your sake and the sake of the baby, and for the sake of the dad.

[aria1234]

if i ovulated on the 29th, how could the sex that happened on October 5th be possible if the egg only last 36 hours? i guess that sort of confused me. The information i read usually has early ultrasounds measuring behind not ahead like in my case if the sex from the 5th was the result of my pregnancy.. what do you think? Your input and advice is helping so much

[AnnieBrooke]

Is the sex you are worried about the October 4 date?  The margin for error in the 8th week when using an ultrasound to date a pregnancy is said to be from one to three days.  Let's say it was the max (about three days), it pushes the October 4 guy to October 1.  If you did ovulate on the 29th, the egg would last about 36 hours.  That's why I say to do a DNA test.  But it sounds like you squeaked by.

[aria1234]

Thank you, It was entirely based on my ultrasound and my boyfriend is so extremely happy...

[AnnieBrooke]

Probably not.  If your ultrasound that gave you the due date was later than your 8th week, or if your doctor gave you the due date based on a little wheel or a calendar and not on your ultrasound, you might have more reason to be nervous.  But if the estimated due date was entirely based on the embryo's measurements and developmental markers at 8w4d, the margin for error does not quite stretch far enough to reach October 5 from September 29 in your 8th week.  It is a close thing, though, and you should get a DNA test once the baby is born to put the issue absolutely to rest.