Found this on another site. Implantation happens as early as 3 dpo.

This link was posted by a medical student???
Endotext.com - Female Reproductive Endocrinology - Premenstrual Syndrome

Haven't read the entire article yet but I thought BFP start showing once implantation happens wouldn't we start getting BFP's by 5dpo or 6dpo

It says in there further down about the HCG levels entering maternal system will try and copy it here. I have heard some people claim they have had a BFP as early as 6 days but never believed it lol

had a quick read and couldn't see where it says that it happens as early as 3dpo?

Off to work soon but will take some screen shots :)

MM I think this student wasnt reading it properly (as did I when I read it briefly!) She swears she is right now and claims her professor said so too but mmmmm I am not sure. It does say, though that it can take as little as 3 days for it to travel down to the uterus?? I thought it took around 5/6 days (same time implantation happened?)

I read some info that says it takes 7-10dpo for it travel down the tube and then once in the uterus it implants.

I can tell you from doing IVF that the vast majority of embryos do not hatch until 5 days at the very earliest and usually say 6 after ovulation, which is egg retrieval day for us. It cannot implant and make HCG until it hatches from its shell. The earliest we ever see a BFP after transfer, 5 days after O, is 4 days later and that is usually only a twin pregnancy- 9 days past ovulation is the equivalent. many get BFPs 10 days past O. Not possible at even 6 days past at all on a stick. Blood test could show a BFP earlier.

Gotta agree w/ NBP, I've transferred several times using 3 day embabies and none of them where hatching, or even close to hatching, shoot they all were only 8 cells, 10 the most (morula's). I've transferred some 5 day embabies and none of them where hatching, but you can do a google search and see some 5 day (some 6 or 7 day embabies) hatching (hatching is where they break out of the 'shell' to attached to the uterus).

I don't believe it, but again, there is so much we don't understand about ourselves :) .