Non-invasive prenatal testing has transformed prenatal screening worldwide by analyzing cell-free maternal and placental DNA. However, clinicians occasionally encounter persistent unreportable results due to genomic noise. Recent investigations reveal that unexplained assay failures can indicate occult maternal malignancy in NIPT. When circulating tumor DNA mixes with normal circulating fragments, it disrupts genomic sequencing metrics. Therefore, obstetricians must understand these complex genomic signals. This article examines recent cohort findings, diagnostic pathways, and best practices for managing abnormal screening profiles.

Biological Mechanisms Linking Maternal Malignancy in NIPT

Prenatal cell-free DNA screening evaluates circulating DNA fragments to detect common fetal aneuploidies. Approximately ninety percent of circulating cell-free DNA originates from maternal hematopoietic cells rather than placental trophoblasts. Consequently, systemic maternal processes directly alter the background plasma sequencing environment. When an occult neoplasm develops, necrotic or apoptotic malignant cells shed abnormal genomic fragments into maternal circulation. These circulating tumor DNA fragments frequently carry wide somatic aneuploidies, amplifications, or deletions. As a result, sequencing algorithms detect chaotic genomic imbalances across multiple chromosomes. Clinical laboratories often report these complex sequencing profiles as persistent noisy signals or uninterpretable test failures. Rather than reflecting technical errors, these results represent biological noise generated by tumor-derived copy number variations. Furthermore, malignant cells produce discordant genomic signatures that mask normal placental signals. In contrast to benign copy number variations, malignant genomic profiles usually exhibit multiple fragmented imbalances across multiple autosomal chromosomes. Consequently, clinicians must recognise that recurrent failed assays may uncover maternal genomic instability rather than simple assay dysfunction. Prompt recognition of this biological mechanism allows teams to initiate appropriate oncological triage without undue delay.

Findings from the Hong Kong Cohort on Genomic Aberrations

A comprehensive clinical investigation conducted between 2020 and 2023 evaluated 84,446 prenatal tests in Hong Kong. Among these tests, 151 samples demonstrated persistent noisy signals, representing an incidence rate of 0.18 percent. Researchers successfully followed up on 131 patients with persistent unreportable results. Importantly, five of these women received a confirmed diagnosis of maternal cancer, establishing an incidental malignancy rate of 3.82 percent within the noisy cohort. Across the overall screening population, the incidental cancer detection rate was 0.006 percent. Genetic analysis revealed that all five confirmed cancer cases exhibited three or more distinct chromosomal aberrations on repeat testing. Specifically, univariate analysis identified significant differences in Tag-score frequencies for chromosomes 18 and 21 between cancer and non-cancer groups. In particular, chromosome 18 involvement appeared consistently across every confirmed oncology case. Although three affected mothers eventually delivered healthy infants, most women presented with advanced malignant disease requiring immediate systemic therapy. Thus, these data confirm that complex multi-chromosomal disruptions serve as strong clinical predictors for maternal oncological disease. Clinicians should therefore interpret recurrent multi-aneuploidy reports with high diagnostic suspicion.

Diagnostic Workup and the Role of Whole-Body MRI

When repeat non-invasive screening demonstrates multiple persistent chromosomal anomalies, physicians must systematically evaluate maternal health. First, clinicians should perform a comprehensive physical examination, detailed personal history, and targeted laboratory evaluations. Basic investigations must include complete blood counts, peripheral blood smears, liver panels, and serum lactate dehydrogenase. However, standard physical exams and conventional laboratory studies frequently fail to detect early or deep-seated tumors. Therefore, specialists strongly recommend whole-body magnetic resonance imaging as the premier non-invasive diagnostic modality. Whole-body diffusion-weighted MRI avoids ionizing radiation, making it completely safe during all trimesters of pregnancy. This advanced imaging protocol provides high sensitivity for detecting occult hematological malignancies, breast carcinomas, and retroperitoneal tumors. In addition, targeted ultrasound of the breasts, abdomen, and pelvis can complement systemic magnetic resonance evaluations. If imaging uncovers suspicious lesions, tissue biopsy remains essential to secure definitive histopathological confirmation. Furthermore, clinicians must perform invasive fetal diagnostic testing, such as amniocentesis, to confirm normal fetal karyotype and exclude true fetal aneuploidy. Accordingly, this structured radiological and cytogenetic pathway ensures accurate maternal staging while safeguarding ongoing fetal well-being.

Pre-Test Genetic Counselling and Ethical Considerations

Comprehensive pre-test genetic counselling forms the cornerstone of ethical prenatal screening programmes. Prior to sample collection, clinicians must explicitly explain that cell-free DNA sequencing tests maternal circulation rather than isolated fetal tissue. Consequently, patients must understand that testing might occasionally uncover unexpected maternal medical conditions, including occult cancers. Discussing these potential incidental findings helps prevent severe psychological shock if a non-reportable or atypical result emerges. Moreover, counsellors should discuss the potential need for extensive diagnostic imaging and oncological evaluations before ordering testing. When laboratory reports signal persistent technical failure due to genomic noise, post-test counselling requires immense empathy and clarity. Clinicians must clearly differentiate between true fetal aneuploidy and maternal genomic alterations to reduce parental anxiety. In addition, care teams must respect maternal autonomy and personal preferences regarding disclosure and subsequent diagnostic evaluations. While some mothers welcome early cancer detection, others experience profound anxiety and distress. Therefore, healthcare providers should deliver comprehensive psychological support alongside clinical evaluations. Establishing transparent communication early ensures patients navigate complex diagnostic uncertainty with greater confidence and informed consent.

Standardising Multidisciplinary Care for High-Risk Cases

Managing occult malignancy discovered during pregnancy requires coordinated collaboration across several medical specialties. Obstetricians, maternal-fetal medicine specialists, medical oncologists, radiologists, and geneticists must form a dedicated multidisciplinary tumor board. Together, this team determines the optimal timing and safety of maternal therapies without compromising fetal survival. Fortunately, oncologists can administer selected chemotherapeutic regimens safely during the second and third trimesters of pregnancy. However, systemic treatments during the first trimester carry high teratogenic risks and require careful individualised deliberation. Additionally, maternal-fetal medicine specialists must closely monitor fetal growth, amniotic fluid volume, and placental function throughout oncological treatment cycles. Coordinated delivery planning helps optimize maternal staging interventions and avoid unnecessary iatrogenic prematurity. Whenever feasible, delivery should occur in a tertiary medical center equipped with high-level neonatal intensive care facilities. Furthermore, longitudinal clinical registries and standardised reporting frameworks remain critical to refine clinical management algorithms globally. By harmonising diagnostic pathways and multidisciplinary treatment protocols, health systems can achieve favorable maternal oncological outcomes while preserving healthy term deliveries. Continuous education among practicing obstetricians ensures swift referral to specialized centers when suspicious genomic results occur.

Why can non-invasive prenatal testing fail to yield a reportable fetal result?

Non-invasive prenatal testing analyzes circulating cell-free DNA derived from both the placenta and maternal tissues. A test may fail or return an unreportable result when sequencing algorithms detect chaotic genomic signals. In most instances, low fetal DNA fraction, maternal obesity, or technical laboratory factors cause assay failure. However, persistent noisy signals across repeat samples often indicate biological maternal abnormalities, including constitutional copy number variants, uterine leiomyomas, or circulating tumor DNA from undiagnosed occult maternal neoplasms.

What diagnostic steps should clinicians follow after detecting multiple chromosomal aberrations?

Clinicians should first verify fetal well-being and exclude fetal aneuploidy using diagnostic amniocentesis. Next, doctors must perform a detailed maternal clinical history, physical examination, and comprehensive laboratory panels. If unreportable genomic noise persists on repeat testing, clinicians should recommend whole-body diffusion-weighted magnetic resonance imaging. This radiation-free imaging modality thoroughly evaluates lymph nodes, solid organs, and soft tissues. Finally, targeted tissue biopsy of any detected lesions confirms histopathology, allowing oncologists to initiate prompt staging and multidisciplinary treatment planning.

Is cancer treatment safe for the pregnant patient and developing fetus?

Cancer management during pregnancy depends strictly on gestational age, tumor stage, and histological subtype. During the first trimester, surgical resection represents the safest intervention, whereas systemic chemotherapy poses substantial teratogenic risks. However, oncologists can safely administer many standard chemotherapy agents during the second and third trimesters without increasing major congenital malformation rates. A coordinated multidisciplinary team balances maternal oncological survival against fetal health, carefully timing maternal interventions to avoid premature delivery whenever clinically possible.

Disclaimer: This content is for informational and educational purposes only and should not be considered medical advice. Health professionals should exercise their independent clinical judgment. Refer to the latest local and national guidelines for clinical practice.

References

1. Chan YYY et al. Incidental detection of maternal malignancy in non-reportable results from non-invasive prenatal testing: experience in Hong Kong and literature review. Hong Kong Med J. 2026 Oct 22. doi: 10.12809/hkmj2513970. PMID: 42908122.
2. Turriff A, et al. Evaluation of Occult Maternal Malignancies Identified by Prenatal Cell-Free DNA Screening. N Engl J Med. 2024;391(22):2110-2121.
3. Amant F, et al. Amsterdam UMC Comprehensive Recommendations for the Clinical Management of Pregnant Women With Noninvasive Prenatal Test Results Indicative of Maternal Malignancy. JCO Oncol Pract. 2024;20(8):1025-1033.