[Analysis of two false positive cases from noninvasive prenatal testing]

Area of Science:

• Genetics
• Prenatal Diagnostics
• Molecular Biology

Background:

• Non-invasive prenatal testing (NIPT) is a screening tool for fetal aneuploidies.
• False positive results can lead to unnecessary anxiety and invasive procedures.
• Accurate diagnosis requires confirmation with traditional methods.

Observation:

• Two cases of NIPT false positives for fetal aneuploidy were analyzed.
• Case 1: Suspected XO (+++) resolved as super female syndrome (47,XXX/46,XX) due to confined placental mosaicism.
• Case 2: Suspected Trisomy 18 (1/20) XO(+) confirmed as Turner syndrome (45,X mosaic).

Findings:

• Confined placental mosaicism can cause false positives for sex chromosome aneuploidies.
• Mosaic forms of Turner syndrome can be misidentified by NIPT.
• Massively parallel genomic sequencing (MPS) and FISH are vital for confirmation.

Implications:

• NIPT for fetal aneuploidy carries a risk of false positives.
• Accurate diagnosis necessitates a combination of cytogenetic and molecular techniques.
• Confirming NIPT results is essential for appropriate prenatal care.