Please help me understand - LP and testing

[Fee]

Okay, so I'm trying to understand the process of conception and have read up all about it. For example, how 5 days after fertilisation the cells do "this", after 6 days the cells do "that", the blastocyst takes another 4-6 days to embed in the endometrium, 14 days after fertilisation the blastocyst becomes an 'embryo' etc etc.

So does this timeframe happen approx the same for every woman no matter how long her LP is?

I know you're supposed to wait until AF is due to test.

For example, what about some people who have a short LP and FF tells them to test on CD34 (11DPO). But then other people may have a longer LP and FF says to test on CD39 (16DPO). What I'm trying to ask is, if the cells do certain things 4 days after fertilisation and the blastocyst becomes an 'embryo' 14 days after fertilisation, why can't everyone test around 14DPO?

Hope you understand what I'm trying to ask.

Am I missing something?! I don't get it!!! I'm very curious! Hope you can help.

[Tanya]

Yep, you have it right. I think FF just advises you to test when AF is late, if you have a longer LP you may be wasting tests by testing before AF, even though other women may be advised to test already just because they have a shorter LP.

Urgh, I hope that made sense! LOL

[butterfly_warrior]

Casting a little bit of IVF experience on things here - it takes 5-6 days for a blastocyst to develop and this is true for all women. My FS was talking about culture media that sometimes works slower and how his scientists weren't comfortable with growing an embryo for 7 days before transer, but I digress!

The time that FF suggests to wait is merely so that you are sure that AF is late and that there is actually a point to testing. If someone normally has a 15 day luteal phase, they could probably test at 14DPO and get a result, but constantly testing before AF is due gets expensive. It would seem rather pointless to test at 14DPO only to get a negative and have AF arrive the next day. If someone normally has a 12 day luteal phase, they are late if they get to 13DPO with no AF, but this doesn't necessarily mean that a pregnancy test will show a clear positive at that time. The testing dates that FF suggest are merely a suggestion and I believe they are set at those times to try to reduce the heartbreak of seeing a BFN and having AF arrive the next day. An attempt to get women to only test when there's a real chance of them actually being pregnant. Like we'd actually wait!

BW

[Fee]

I am still confused!

Just saying randomly, if a baby implants at 7DPO (for example - just throwing random info out there) why does it matter if your AF is due 8 days later than someone else.

So say there's two women. Both O-ed on CD19 but one woman's AF is due around CD34 and the other CD40.

Why can't they both test on the same day? CD34? If they both had a baby implant at 7DPO? Why does the woman with the longer LP have to wait until CD40 to test?

Just found this on Birth.com.au:

Once your baby fully implants, they start to release a hormone called 'human chorionic gonadotrophin hormone' (or 'HCG') into your blood stream. The HCG level initially starts off very low, but rapidly increases (doubling every second day), so that within a few days to a week or so, the HCG level becomes high enough to be detected in your blood stream and urine. It is this increasing level of HCG that forms the basis of blood and urine pregnancy tests. This is also why pregnancy tests do not show up as being 'positive' until the woman's period would have been due (and why women do not start to feel the physical signs of pregnancy until after this time).

So if the baby implants at so many DPO, what on earth is it doing for the other number of days for the woman with the extra long LP? Once it is implanted the HCG is going into the blood stream.

[Tanya]

why does it matter if your AF is due 8 days later than someone else.

It doesn't, the embryo will still be releasing HCG into your blood...

Why can't they both test on the same day? CD34? If they both had a baby implant at 7DPO? Why does the woman with the longer LP have to wait until CD40 to test?

They can... but the woman who's af is late has some evidence to test, so more reason to believe she is pg. The woman who is still waiting to see if AF is going to arrive has no evidence to suggest she is pg yet. That is not to say she can't test... but it may be a waste of a test because she has no evidence that she may be pg.

So if the baby implants at so many DPO, what on earth is it doing for the other number of days for the woman with the extra long LP? Once it is implanted the HCG is going into the blood stream.

The longer your lp the better chance you have for a sticky baby...

Does that help?

[Fee]

Don't worry! I get it now!

I have been focussing on if you ARE pregnant.

But in case you're not pg, then obviously you're better off waiting until AF is due. I get that.

Man I was in bed trying to get to sleep when I finally got it and I had to get back up to come on here and explain myself!

I just wasn't thinking of the "if you're not pg" scenario. Silly me. DOH.

Thanks everyone. God I'm dumb. Maybe I am pg now! LOL