@Hopewishprayer I think it depends on the area. In my area at the same appointment they do the blood tests for Downs etc and also they check the neck for that I think this needs to be done by 14 weeks but not 100%. In some areas I have heard they do the blood test separately.
On my first I was 13 weeks but they moved me back a few days as well I guess the issue would come if you are potentially measuring over 14 weeks at the time. Is there a number on the letter you could call to see if you could get an earlier appointment? X