I was hoping that some of the mamas here would interested in doing something that might be an interesting experiment. I'm especially hoping some of the first time mamas would interested.
What I'd like is for you to make a post with all your "due dates" and see which ends up being the closest. The 3 main ones I was thinking of are: Naegle's method - this is the standard method (but seriously out of date and wrong, esp for first timers) of dating used by doctors and a lot of midwives. It's the one that the little wheels are based on
Ultrasound date - assuming you have an early ultrasound and are given a date based on it
Mittendorf-Williams - this is newer method based on current research, the studies showed it was a lot more accurate than Naegle's
Additional possibilities if you know ovulation date could be calculating Naegle & Mittendorf-Williams from ovulation instead of from LMP.
To calculate using Naegle's method for yourself (or you could use just about any online calculator) it is LMP + 9 months + 7 days.
To calculate using the Mittendorf-Williams method take the first day of your last period and subtract three months. Then you add fifteen days if this is your first baby and you are Caucasian. If you are not Caucasian or this is not your first baby, you will want to add on ten days.
The easiest way to calculate using ovulation is to just add or subtract the number of days your ovulation differed from the "standard" 14 days.
My due dates (based on LMP):
Naegle's method (from http://www.josephsunny.com/medsoft/nagel.html) : Jan 14, 2012
Today's Parent & BabyCentre due date calculator Jan 12, 2012
Mittendorf-Williams: Jan 17, 2012
Based on ovulation:
Naegle: Jan 16, 2012
Common due date calculators: Jan 14, 2012
Mittendorf-Williams: Jan 19, 2012
Hope some other people want to play along! :)