Private Nipt Test

I wouldn’t skip the 12 weeks screening on nipt alone. I had harmony done but was recommended to still attend 12 weeks scan. Where I did my harmony, I got my nuchal scan included anyway so I could have forgone the nhs screening. At the 12 weeks combined screening, they check for more than just probabilities for trisomy 18/21/23. They check for other defects eg spinal bifida etc.
Do let nhs know your results and they can take it from there.

I did the test, purely because it was included in my ivf though!

PAPP A is to do with the functioning of the placenta and it isn't tested with NIPT tests.

I declined the nipt test on this basis, it seemed wasteful. they have a script they need to run through on declining etc but it was fine

That's great news about your test. When you go for your 12 week scan you need to tell them about the results as they will override any screens the NHS do, but they will still want to do the blood test as it tests for PAPP-A levels, which NIPT doesn't.