Validation study of MaterniT21 in twins, triplets; To determine whether MaterniT21 can reliably identify the core trisomies (T21, T18, T13) in twin and higher order multiple pregnancies • International collaboration of 27 prenatal diagnostic centers • 25 twin pregnancies, 2 triplet pregnancies • 7 twin pregnancies with Trisomy 21, 1 with Trisomy 13, and a