Maternal age (MA) 30%
MA and maternal serum biochemistry at 15–18 weeks 50–70%
MA and fetal nuchal translucency (NT) at 11–13+6 wks 70–80%
MA and fetal NT and maternal serum free b-hCG and
PAPP-A at 11–13+6 wks 85–90%
MA and fetal NT and fetal nasal bone (NB) at 11–13+6 wks 90%
MA and fetal NT and NB and maternal serum free
b-hCG and PAPP-A at 11–13+6 wks (to je DHT) 95%