LMP, and no the U/S can not tell if your period was or was not implantation bleeding.. It is just a guess, a good one most of the time but that's why the EDD is an estimate.. Many women are irregular or don't know for sure their LMP but they know the month.. You could be two weeks ahead of that date or two weeks behind..
Conception is hard to determine because it can take a few days or up to 12 for the egg to attach to the uterus. Most conceptions happen in the tubes and then time is needed to travel down.. Confusing huh :)
at 5:51 PM on May. 24, 2011