hi
i cant help you too much but when i was pregnant with Bellah when we had out ultrasound done the nuchal fold measurement (NT) came back at 4.2mm if it is above 3.5mm that is when futher testing is required for down syndrome and heart problems. We got told with this measurement she was guarenteed to be down syndrome however she was born without it and with no heart problems so far, everything is just statistics but from what you have said your measurements are fantastic!