I KNOW the exact day I conceived too! (Because it was the only day my husband and I didn't take precautions) My doctor didn't really care when the calculations I gave him were different to the ones from the ultrasound.

The thing that really bothers me, is that the hospital will try to induce you based on the ULTRASOUND - they don't really care what I tell them. I have had this same problem with 4 of my children. They all go technically 'overdue' and I have to fight the doctors off with when they try to induce me. It will probably be the same with baby number 5.

Luckily, because I have had 4 uncomplicated (yet 'overdue') births - the doctors have decide to give me the benefit of the doubt. (with the last baby anyway).