I had mine at my 16 week appt, but I think it can be done from week 14. It just has to be the second trimester, so I am sure those dates are fine.
I had mine last Wed, and they said if I haven't heard by yesterday then it should mean I am not high risk. Should is not certain so I won't rest until I have the phonecall or letter, but I am hoping that means it's good news.