Analysis of cases with prenatal diagnosis of mosaicism: Indications, methods of prenatal diagnosis, and pregnancy outcome follow-up.

OBJECTIVE

This study aims to analyze prenatal diagnostic indications, methods, and prognosis of fetuses with mosaicism, providing a reference for related prenatal diagnosis and genetic counseling.

METHOD: Cases of fetuses prenatally diagnosed with mosaicism via amniocentesis at our center over a 3-year period were retrospectively reviewed. The review covered maternal age, prenatal ultrasound phenotypes, results of whole-genome non-invasive prenatal testing (wgNIPT), and outcomes of prenatal diagnosis, including karyotype analysis, chromosomal microarray (CMA), and fluorescence in situ hybridization (FISH). Pregnancy outcomes and postnatal phenotypes were also examined.

RESULTS

Among the 37 cases reviewed, 43% (16/37) involved women of advanced maternal age (≥35 years), while 22% (8/37) exhibited ultrasound abnormalities. Of the subset of 31 cases that underwent wgNIPT prior to amniocentesis, 94% (29/31) had results concordant with prenatal diagnostic findings. A total of 35 cases were analyzed using multiple techniques, with 17 showing consistent findings, 10 discrepancies in mosaic or non-mosaic status, and 8 conflicting results across methods. Thirteen cases resulted in live births with no apparent abnormalities detected in follow-ups at ages 3-5.

CONCLUSION

wgNIPT is a valuable tool for prenatal mosaicism screening, although its detection of complex cases remains limited. Prenatal diagnosis of mosaicism requires the mutual verification of multiple genetic techniques. Postnatally, mosaicism might lack apparent phenotypes; prolonged monitoring is needed to detect delayed effects.