My nuchal u/s came back high risk 1:52 my baby has downs. Just wondering what exactly my percentage is and what happens next?

Next steps depend on. whether you had combined 1st trimester screening test or integrated screening. For the latter, you'd have blood drawn in both the 1st & 2nd trimesters. You may have a Fetal Ultrasound for other anatomical markers of DS & a test of fetal DNA circulating in your blood. If your calculated risk remains high, you'll be offered a diagnostic test for Fetal Chromosome Analysis & genetic counseling.
Probability. 1:52 is a high risk number, so your chances of this pregnancy actually resulting in a baby with Down syndrome is 1 out of 52 pregnancies, or about 2% chance. While that number seems low, the age-adjusted risk for young mothers (20-25yrs old) in the USA is more like 8 per thousand, or 0.8 % - the test is telling you your pregnancy carries a risk almost 3 times the normal risk for your age group.