The process is that pregnancies are first screened for risk, a statistical analysis; only high risk pregnancies are usually offered a definitive diagnostic test, since amnio and CVS carry significant risk relative to the probability of a diagnostic positive. There is less invasive testing of cell-free DNA from the mother’s blood, but I think reliable protocols for this are fairly recent.
So what you say is not necessarily a reliable inference. The relevant statistic would be the proportion of positive post-natal diagnoses that were screened negative, which oddly I can’t find anywhere. If I were a parent, I would very much want to know all the conditional probabilities.
That part reported by the OP that’s truly BS is that there’s something in UK law against Down syndrome. There isn’t. The law in the UK doesn’t require abortion in cases of Down syndrome, nor does it disallow anyone with Down syndrome from entering the country. The 90% figure is due to choice, not legal mandate. And it’s 90% of known pre-natal cases, not 100% of all cases. As I said before, this is the UK, not Nazi Germany.
BTW, it’s interesting how self-selection biases the stats. Parents who know they wouldn’t have an abortion are a lot less likely to get the test. It’s a good example of how one must be careful to avoid selection bias when doing statistical analysis.
And this is an example of how one must be careful to avoid an assumption of self-selection bias with an inference of motivation without reading the prior post…
Given that this thread was started by a troll who has now been banned, I’m going to close this. If anyone would like to further discuss any factual matters pertaining to this thread, PM me and I will re-open it.