The FASTER (First and Second Trimester Evaluation of Risk) Trial is a multicenter prospective study comparing the accuracy of first and second trimester non-invasive screening methods for Down syndrome and other aneuploidies to diagnosis at delivery or miscarriage/fetal loss). All women will receive the two non-invasive test batteries in both the first and second trimesters. The accuracy of the results of different combinations of non-invasive tests will be compared with diagnosis at delivery or at miscarriage or later fetal loss.