Application of mosaicism ratio to multifetal gestations

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