Estimating Your Conception Date Without a Last Menstrual Period (LMP)

Question
I've read all the calculations on finding out when you are due and when you conceived but they all revolve around a lmp. for the life of me i can not remember when or if i had a period. I want to find out the day i conceived. is there any other guestimation. or can only a doctor tell me?. thanks

Answer
If you are still very early, less than 10 weeks, you can have an ultrasound done.  Early ultrasounds can date a pregnancy with 3-5 days of accuracy, and this would pinpoint your conception date to within about a week.

If you are already past your first trimester, there just isn't any way to accurately date your pregnancy.  You can't even calculate back from the baby's birthday, because normal gestation can be anywhere from 37 to 42 weeks, giving a full month's range of possibilities for conception.