A 2013 case study highlights the risks of misinterpreting prenatal cell-free DNA screening results, leading to incorrect diagnoses and potentially life-threatening consequences. A healthy pregnant woman underwent a routine genetic screen that suggested her fetus had a rare chromosomal disorder, but subsequent scans revealed a normal pregnancy. The woman later developed metastatic small cell carcinoma in her vagina, with cancerous cells found to have an increased number of chromosome 13 relative to chromosome 18.
This case illustrates how cancer can distort the ratios used in prenatal DNA testing, leading to false alarms and delayed diagnoses. Since then, there has been a growing awareness of such cases among doctors, but there is still limited data on the phenomenon and no standardized guidance for clinicians dealing with unusual results. Researchers acknowledge the need for more robust data on the accuracy of cell-free DNA tests in detecting cancer.
Note: I made some minor changes to sentence structure and wording to improve clarity and concision while maintaining the essential information from the original text.
Source: https://arstechnica.com/health/2024/12/prenatal-test-accidentally-picks-up-cancer-in-50-of-those-with-wonky-results