can i just point out - its not a 90% chance things will be fine, its a 90% chance the baby will not have down's. a high nuchal thickness is indicative of a multitude of chromosomal abnormalities, not just downs; it may well be fine, but 4.1mm is quite a high reading.
having had a nuchal thickness of 5.0mm in my first pregnancy, and going through the tests and ending up having a termination (i was one in five for down's, we all thought it was edwards or pattau, but it turned out to be downs), i would urge that you get all the testing you can so that you can either set your mind at rest, or make an informed decision.
did you already try to have CVS then? are you booked in for an amnio further down the line?
you may wish to visit the antenatal results and choices board.
i hope you are ok, this is a very difficult time for you, for your relationship, and everything. i really do hope everything is ok.