It all depends how you estimate your EDD also. I used the more accurate one where the legnth of my ovulation cycle and lunar cycle are taken in to account and this placed my EDD as 9 days after the method used by Obs. A woman who has a longer menstrual cycle has a longer gestation and this is something my MIL told me years ago but I hadn't heard around birthing circles until recently. Also, you might like to ask the women in your family how long they gestated for. Some women naturally gestate longer (or shorter) and it can run in families. IMO a woman is not overdue until she is past 42 weeks.