Abstract Objective Outcome data from cell‐free DNA (cfDNA) screening in twin gestations are limited.

Evaluate the cfDNA screening no-call rate based on maternal weight, and assess optimal timing to repeat a test in women with an initial no call result

Examine the behavior of mosaicism ratio in multifetal gestations applied to chromosome aneuploidy and fetal sex • For multifetal gestations, MR can be applied to cases positive for aneuploidy, to determine if one or more fetuses are affected, and cases where Y chromosome material is detected to determine if one or more fetuses are male • For positive resu

Validation study of MaterniT21 for Trisomy 18 and Trisomy 13 • International collaboration of 27 prenatal diagnostic centers  • 4,664 singleton pregnancies • 62 pregnancies with Trisomy 18: Detection rate for Trisomy 18 = 100% (59/59), Trisomy 18 false positive rate – 0.3% (5/1,688) • 12 pregnancies with Trisomy 13: Detection rate for Trisomy 13 = 91

Clinical experience with copy number variants (CNVs) via MaterniTGENOME