Objective: To review the clinical data of a fetus with false positive result of non-invasive prenatal testing (NIPT) due to confined placental mosaicism (CPM).
Methods: Amniotic fluid sample was taken from a pregnant women with high risk for chromosome 16 aneuploidy for karyotyping analysis, single nucleotide polymorphism array (SNP array) and interphase fluorescence in situ hybridization (FISH). Genetic testing was also conducted on the fetal and maternal surface of the placenta, root of umbilical cord and fetal skin tissue after induced abortion.
Results: Cytogenetic analysis of the amniotic fluid sample yielded a normal karyotype. SNP array revealed mosaicism (20%) of trisomy 16 in the fetus. FISH confirmed the presence of mosaicism (25%) for trisomy 16. After induced labor, all sampled sites of placenta were confirmed to contain trisomy 16 by SNP array, while the analysis of fetal skin tissue yielded a negative result.
Conclusion: CPM is an important factor for false positive NIPT result. Prenatal identification of CPM and strengthened pregnancy management are important to reduce adverse pregnancy outcomes.