I came across this website, found it very interesting and thought I would share:
https://spacefem.com/pregnant/charts/duedate0.phpIt also cites to a bunch of other actual medical studies...the lady here is just doing an informal survey which is hardly scientific, but is a survey of over 6k women. She has several graphs she uses to show her stats. The actual studies she cites to seem to suggest that the standard deviation is about 9-10 days either way from your due date. In other words, about 70% of women (I think 1 SD = 68.26%) of women will give birth on their due date or within 9-10 days before or after their due date.
I thought it was also good to illustrate that a lot of women go well past their due date.
IF DX: DOR & Fragile X pre-mutation carrier
2011: FSH 13.3 & E 99; AMH 0.54
2nd FSH 6.2 E 40's AFC: 8
BFP from Clomid/IUI ~ Pre-e and IUGR during pregnancy ~ DS born 9/4/12
Feb./March 2013: AMH less than 0.16 (undectable) and AFC = 4;
BFP from supps ~ DS#2 due May 2014
May 2014 January Siggy Challenge:


Re: When will I have my baby?
2011: FSH 13.3 & E 99; AMH 0.54 2nd FSH 6.2 E 40's AFC: 8
BFP from Clomid/IUI ~ Pre-e and IUGR during pregnancy ~ DS born 9/4/12
Feb./March 2013: AMH less than 0.16 (undectable) and AFC = 4;
BFP from supps ~ DS#2 due May 2014
May 2014 January Siggy Challenge: