Presence of fetal DNA in maternal exhaled breath condensate.

Objectives: Cell‐free DNA has been found in all body fluids, but DNAs emerging from locations that are not in direct contact with breath in exhaled breath condensate (EBC) are yet to be found. The potential of EBC for prenatal and cancer screening prompted us to investigate whether fetal DNA is present in maternal EBC. Method: A total of 20 pregnant women's EBC and blood samples were collected. Four Y chromosome‐specific assays were tested on all EBC and plasma samples by quantitative PCR (qPCR). The best‐performing assay was used for digital droplet PCR (ddPCR) on all EBC and the six plasma samples. Results: The sex of the fetuses was accurately determined from plasma samples. DNA sequences could not be properly amplified in EBC samples by the qPCR. By ddPCR, the Y chromosome sequence was amplified in two of the 11 EBC samples, from women carrying male fetuses (2/11), and the Y chromosome sequence was not amplified in the EBC of women carrying female fetuses (9/9). Exhaled breath condensate ddPCR result's specificity was 100%, the detection rate of Y chromosome was 18.18% (2/11), and the corrected accuracy was 59.09%. Conclusion: Our finding of "the presence of fetal DNA in maternal EBC", despite the low detection rate, might have a major impact on prenatal diagnosis and cancer screening. Key points: What's already known about this topic? DNA/RNA sequences of lung cancer, Mycobacterium tuberculosis, and SARS‐Cov‐2 were detected in exhaled breath condensate (EBC). Cell‐free DNA (cfDNA) has been detected in various body fluids like blood, urine, cerebrospinal fluid, sweat, and breast milk, and cell‐free fetal DNA (cffDNA) has been shown in maternal plasma. Also, the lungs are thought to be filters of fetal cells in the maternal circulation. What does this study add? This is the first study that showed the presence of Y chromosome sequence in the EBC of a woman carrying a male fetus. Additionally, the presence of a DNA sequence that does not belong to the gastrointestinal tract or respiratory system in the breath has not been shown until now. The findings of this study may have an impact on non‐invasive prenatal diagnosis and cancer screening. [ABSTRACT FROM AUTHOR]