I was reading on a site that was suggested by another member awhile back and here it said that (example) if she ovulated on day 11 then conception would be on day 13 because it takes 48 hours for the egg to ripen...So maybe that would be giving you a few days? Just trying to help...This is the site that I found the info on.
http://www.debbiejensen.com/due_date.html
My Mom's dog Millie is due October 3rd with 7, So I'm trying to gather as much info as I can to help her.