A rare case of NIPT discrepancy caused by the placental mosaicism of three different karyotypes, 47,XXX, 47,XX,+21, and 48,XXX,+21

BACKGROUND: Placental mosaicism is one of the major reasons for noninvasive prenatal testing (NIPT) discrepancy. Herein, we discovered a rare case of placenta with complex karyotypes that caused false‐positive and false‐negative results in noninvasive prenatal testing. METHODS: Next‐generation sequencing (NGS) and Quantitative fluorescent polymerase chain reaction (QF‐PCR) were performed on the cord blood sample, fetal tissues, and eight placental biopsies. Fluorescent In Situ Hybridization (FISH) and karyotyping were also carried to confirm the fetal genome status. RESULTS: The results suggested that the fetal chromosome was 47,XXX and the placenta had three karyotypes of 48,XXX,+21, 47,XX,+21, and 47,XXX. QF‐PCR indicated that the extra chromosome 21 and chromosome X were all from the father. It is speculated that the zygote may have 48,XXX,+21 karyotype and trisomy rescue could be the main mechanism for the development of the homogeneous fetus and complex mosaic placenta. CONCLUSION: Overall, the complicated nature of our case underlines the importance of discussing with parents the possibility of both atypical and discordant results during preconfirmatory amniocentesis counseling and consent.