Published online Aug 26, 2022. doi: 10.12998/wjcc.v10.i24.8641
Peer-review started: December 14, 2021
First decision: May 30, 2022
Revised: June 1, 2022
Accepted: July 18, 2022
Article in press: July 18, 2022
Published online: August 26, 2022
Confined placental mosaicism (CPM) is one of the major reasons for discrepancies between the results of non-invasive prenatal testing (NIPT) and fetal karyotype analysis.
We encountered a primiparous singleton pregnant woman with a rare CPM consisting of 47,XY,+21; 47,XXY; and 46,XY, who obtained a false-positive result on NIPT with a high risk for trisomy 21. Copy-number variation sequencing on amniotic fluid cells, fetal tissue, and placental biopsies showed that the fetal karyotype was 47,XXY, while the placenta was a rare mosaic of 47,XY,+21; 47,XXY; and 46,XY.
The patient had a rare CPM consisting of 47,XY,+21; 47,XXY; and 46,XY, which caused a discrepancy between the result of NIPT and the actual fetal karyotype. It is important to remember that NIPT is a screening test, not a diagnostic test. Any positive result should be confirmed with invasive testing, and routine ultrasound examination is still necessary after a negative result.
Core Tip: We identified that the patient had a rare confined placental mosaicism consisting of 47,XY,+21; 47,XXY; and 46,XY, which caused a discrepancy between non-invasive prenatal testing (NIPT) and fetal karyotype. Although NIPT has high sensitivity and specificity, false negatives and false positives are still possible. It is important to remember that NIPT is just a screening test, and any positive results need to be confirmed with invasive testing. Patients with negative NIPT results still require follow-up ultrasound examination.