Combined test- a combination of NT scan and the blood test is a Screening test. Meaning it will tell you if the baby is at a high or a low risk for the problem however it won't tell you if baby has a problem or not. The people who are at high risk are offered further confirmatory test like CVS or Amniocentesis, people who are intermediate risk may opt for a more accurate blood test called NIPS or NIPT. People who are low risk usually opt not to go for any further testing.
Next Steps
contact a fetal medicine doctor( who specialises in this testing) as accuracy of the results is crucial which can be achieved by experts.
Health Tips
Do not panic majority of the babies are normal. it's always good to be sure.