Couldn't be dated at 12 week scan - NT check / harmony? Confused!

[angelix]

I had my 12 week scan around 10 days ago but baby wouldnt play ball, so couldn't get all the measurements to officially date me.
Baby was measuring 12 weeks at the time, but I've to go back in 2 weeks time for another go and should be dated then.
I just assumed the crown to rump measurement was all they needed, but obviously not.
I'm not overly concerned about the dating, just a bit frustrated as I'd opted to have the downs check and they couldn't get the neck measurement. I've been told I'll need to go for a blood test at the hospital when I'm 14 weeks + as a result, has anyone else had this?
The sonographer mentioned they check four hormones, I'm not sure if this is the same as the harmony test?
If anyone knows or has had a similar experience I'd love to hear from you.
Thanks!

No it’s not the same as the harmony test. Just like the combined test, the quad test is not wholly reliable but a decent indicator for most people (but a huuuuge number of people are told high risk when they are not).
NIPT (Harmony, Panorama etc) is 99% for Downs and different reliability depending on the test for the other major trisomies.

With my first I had to re-do my 12 week. They could clearly measure me approximately but needed exact measurements for dating so had to go back a week and a half later.