Can the double marker test can be done before nt scan at 11 wee?,The doctor took blood sample on 5-mar for double market test before nt scan which is on 14-mar and told me that we will provide consoledated report of double marker test and nt scan at 18-march,so will he preserve the blood till one week, is it fine to preserve the blood or the fresh sample is better. Please guide me at what stage double market test should be done