[Results of screening and prenatal diagnosis for 71 fetuses with high risk for trisomy/monosomy 13 syndrome by non-invasive prenatal screening].

Objective: To analyze the clinical data and results of prenatal diagnosis for fetuses with high-risk for trisomy/monosomy 13 by non-invasive prenatal testing (NIPT).

Methods: Clinical data of pregnant women with fetus at a high risk for trisomy/monosomy 13 by NIPT at the First Affiliated Hospital of Zhengzhou University from May 2016 to May 2024 were reviewed, and relevant data such as Z-score, positive predictive value (PPV) and fetal fraction (FF) were analyzed to assess the correlation between them. This study was approved by the Ethics Committee of the Hospital (No. 2018-YB-08).

Results: 71 fetuses were found to have a high risk by NIPT, including 58 cases for trisomy 13 (T13) and 13 cases for monosomy 13 (M13). 52 women had opted invasive prenatal diagnosis and 13 cases were confirmed, which yielded a positive prediction value (PPV) of 25%. 12 fetuses were confirmed as T13 (PPV = 29.3%; 12/41), 1 was confirmed as M13 (PPV = 9.1%; 1/11). The PPV had increased along with the Z-score. Fetal faction (FF) was not correlated with the age of woman but gestational age, and was negatively correlated with the body mass index. No statistical difference was found in FF and Z-score between true- and false-positive fetuses, and there was a weak correlation between the Z-score and FF. The PPV of the NIPT could be improved by combining the results of ultrasonography.

Conclusion: The high false positive rate for T13 may be related to confined placental mosaicism, PPV is related to the Z-score, which in turn is related to FF. High-risk women are strongly recommended to undergo genetic counseling and prenatal diagnosis. Clinicians should consider relevant information such as the age of women, gestational age, indication for prenatal screening, Z-score, PPV, and FF in order to accurately interpret the result of NIPT, reduce anxiety, and avoid direct termination of the pregnancy.