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Updated: Jan 4, 2026
Pre-Implantation Genetic Testing for Aneuploidy on a Semiconductor Based Next-Generation Sequencing Platform
Published on: August 17, 2022
Cell-free DNA fetal fraction in twin gestations in single-nucleotide polymorphism-based noninvasive prenatal
Herman Hedriana1, Kimberly Martin2, Daniel Saltzman3
1Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of California Davis Health, Sacramento, CA.
Objectives:
The performance of noninvasive prenatal screening (NIPS) for fetal aneuploidy in twin pregnancies is dependent on the amount of placentally derived cell-free DNA, the "fetal fraction (FF)," present in maternal plasma. We report FF values in monozygotic (MZ) and dizygotic (DZ) pregnancies.
Methods:
We reviewed FF in pregnancies at 10 to 20 completed weeks gestational age based on single-nucleotide polymorphism (SNP)-based NIPS where zygosity was routinely established in twin pregnancies. The cohort included 121 446 (96.3%) singleton, 1454 (1.2%) MZ, and 3161 (2.5%) DZ pregnancies. For DZ twins, individual FFs were measured.
Results:
Combined FF for DZ and MZ fetuses were 35% and 26% greater than singletons, respectively. The individual FF contributions from each fetus in DZ twins were, on average, 32% less than singletons. FF in DZ twin pairs were moderately correlated (Pearson correlation coefficient.66). When a threshold of 2.8% FF was applied to define uninterpretable results, 1.7% (2102/121 446) of singletons, 0.8% (11/1454) of MZ pairs, and 5.6% (178/3161) of DZ pairs were uninterpretable.
Conclusion:
For optimal aneuploidy NIPS in twin pregnancies, zygosity should be established and in DZ twins FF for both fetuses should be determined to identify those cases where results can be reliably interpreted.
