You can now test fetal DNA fragments in maternal blood (cffDNA) to detect trisomies with high specificity and sensitivity-- though a positive result is only ~50% confidence, and needs follow-up screening with a riskier method for confirmation. The 0.7% miscarriage risk from follow-up CVS or amniocentesis is more justified in that case.

http://www.nejm.org/doi/full/10.1056/NEJMoa1311037