Application of mosaicism ratio to multifetal gestations

Jill Rafalko, Samantha Caldwell, Erica Soster, Eyad Almasri, Graham McLennan, Tong Liu, Vivian Weinblatt, Philip Cacheris, Ron McCullough
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 results (aneuploidy) in twins: when only one twin was affected with trisomy 21, the average MR of chromosome 21 was about half (52%) of the MR when both twins were affected • For cases in which Y chromosome was detected - When one twin was male, the average MR of the Y chromosome was about half (49%) of the Y MR of two male fetuses