RT Journal Article SR Electronic T1 Non-invasive prenatal testing: use of cell-free fetal DNA in Down syndrome screening JF British Journal of General Practice JO Br J Gen Pract FD British Journal of General Practice SP 298 OP 299 DO 10.3399/bjgp17X691625 VO 67 IS 660 A1 Imran Rafi A1 Melissa Hill A1 Judith Hayward A1 Lyn S Chitty YR 2017 UL http://bjgp.org/content/67/660/298.abstract AB