I am due June 20, 2010. I had an early ultrasound done to determine this because I was not sure of my lmp. I need to know when the baby was conveived and what the chances are to the baby being conceived on the 15th of Sept as opposed to the following week.

My due date is June 20, 2010. What are the chances that I conceived this baby on 9-15-2009?

Please understand that all of pregnancy is a guessing game. If you are worried about paternity it is impossible to tell until a paternity test is done.

Now, with that said... I have my handy dandy gestation wheel here, the same one the doctors use, and your due date is June 20, the approximate day you conceived would be September 28 or 29, and it shows that your LMP was approximately September 15.