Rare Prenatal Duplication on Chromosome 16 Reveals a Genetic Puzzle With Mostly Reassuring Outcomes

A routine amniocentesis test rarely makes headlines, but a new study from Wenzhou Central Hospital in southern Zhejiang, China, offers one of the most detailed long-term looks yet at a genetic finding that has long puzzled doctors and parents alike. Researchers screened 12,038 pregnancies between 2014 and 2025 and identified 19 fetuses carrying a microduplication of a small stretch of chromosome 16 known as 16p13.11. The finding, published in Molecular Genetics & Genomic Medicine, corresponds to a detection rate of roughly 0.16 percent, and it comes with follow-up data stretching as far as ten years after birth. For families facing this diagnosis during pregnancy, the study provides something previously scarce: real outcomes for real children.

The 16p13.11 region is a genomic trouble spot. It is packed with low-copy repeats, segments of DNA that are nearly identical in sequence and sit in repeating blocks along the chromosome. During DNA replication and repair, these near-identical sequences can misalign, and when the cellular machinery recombines the wrong pair, chunks of the genome are deleted or duplicated. This process, called non-allelic homologous recombination, makes 16p13.11 a recurrent hotspot for copy number variants, the gains and losses of DNA segments that underlie a family of genomic disorders. Duplications and deletions in this region have been linked in the medical literature to developmental delay, intellectual disability, language impairment, behavioral abnormalities, attention-deficit/hyperactivity disorder, autism spectrum disorder, distinctive facial features, and cardiovascular anomalies.

What makes 16p13.11 microduplication so difficult is that it does not behave like a classic disease-causing mutation. Many carriers are apparently healthy adults, and the duplication is frequently inherited from a parent who shows no signs of any related condition. Geneticists describe such variants as having incomplete penetrance, meaning not everyone who carries the extra DNA shows effects, and variable expressivity, meaning those who are affected can show very different symptoms. In 2024, the Clinical Genome Resource assigned the region a triplosensitivity score of 2, a rating that suggests moderate but not definitive pathogenic potential when an extra copy is present.

The Wenzhou team used chromosomal microarray analysis, a technique recommended by the American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine for prenatal diagnosis, to scan fetal DNA extracted from uncultured amniotic fluid cells. The platform they used, the CytoScan 750K array, detects copy number changes across the whole genome at high resolution. The 19 duplications they found ranged in size from 0.80 to 1.60 megabases and spanned between 7 and 13 genes cataloged in the Online Mendelian Inheritance in Man database. Every duplicated segment overlapped the critical region associated with 16p13.11 microduplication syndrome, and all coordinates were mapped against the hg19 reference genome.

The reasons the pregnancies reached amniocentesis in the first place were varied and mostly unrelated to the duplication itself. Seven cases were prompted by advanced maternal age, five by a history of adverse pregnancy outcomes, three by high-risk serum screening results, and four by abnormal ultrasound findings. Those four ultrasound cases were strikingly heterogeneous. One fetus had increased nuchal translucency, a thickening of the fluid-filled space at the back of the neck. Another showed a constellation of severe problems: growth lagging about three weeks behind dates, fluid accumulating in both the chest and abdomen, an enlarged heart, and tricuspid regurgitation. A third displayed right upper limb anomalies consistent with radial dysplasia, including a short, curved ulna, an extremely short radius, and marked angling of the wrist. The fourth had a single umbilical artery and an echogenic intracardiac focus in the left ventricle, a bright spot on the heart that is usually benign.

Pedigree analysis, in which both parents are tested to determine whether the duplication was inherited or arose newly in the fetus, was completed in only five of the 19 cases. In four of those five, the duplication came from a phenotypically normal mother or father; one was de novo, appearing for the first time in the child. Notably, after comprehensive genetic counseling, the parents of all five fetuses with confirmed inheritance information chose to continue their pregnancies, a decision the authors emphasize reflects individual family choices rather than a general recommendation.

The pregnancy outcomes and follow-up data form the heart of the study. Three couples, all counseled by multidisciplinary teams, elected to terminate their pregnancies, including two of the cases with severe multi-organ ultrasound abnormalities. The remaining 16 fetuses were carried to term, and postnatal follow-up was ultimately available for 14 children ranging in age from 10 months to 10 years. The picture that emerged was largely reassuring. Five children were reported to be developing ahead of their age-matched peers, and seven showed no abnormalities at all according to their parents. One child, now nine years old, showed delayed development: walking began at 17 months and first words did not arrive until age three, with parents describing average expressive language ability. One infant was hospitalized at birth because of a ventricular septal defect, a hole in the wall separating the heart’s lower chambers, but subsequent examinations revealed no additional problems. Two children were lost to follow-up.

The authors are careful about what these outcomes do and do not prove. The child with developmental delay carried a 1.25 megabase duplication spanning ten genes, including NDE1, a gene with established roles in neurogenesis and the development of the cerebral cortex. That association fits the neurodevelopmental spectrum described for 16p13.11 imbalances. Yet other children in the same cohort carried duplications of similar size or gene content and developed normally, which demonstrates that duplication size and gene count alone cannot predict how any individual child will fare. The region also contains ABCC6, whose loss-of-function variants cause abnormal tissue mineralization, and MYH11, which is involved in smooth muscle and has been linked to cardiovascular disease, but the study found no evidence that extra copies of these genes directly caused the observed heart defect. Background genetic modifiers probably contribute to the variability, though their individual effects remain beyond the reach of this data set.

For prenatal counselors, the practical message is one of calibrated uncertainty. The researchers argue that 16p13.11 microduplication should be presented to expectant parents neither as a benign curiosity nor as a definite diagnosis, but as a susceptibility variant with reduced penetrance and variable expressivity. Interpretation should weave together the fetal ultrasound picture, the characteristics of the duplication itself, parental testing results where available, and family history. An inherited duplication from a healthy parent is somewhat reassuring but does not eliminate risk, while a de novo duplication or one accompanied by significant structural abnormalities warrants a broader discussion of possible outcomes. After birth, the authors recommend surveillance guided by the child’s clinical course rather than the laboratory result: close monitoring of speech and motor milestones, attention to learning and behavioral concerns as the child grows, and cardiac review when indicated, since some effects may only surface later in childhood or adulthood.

The study’s limitations are acknowledged candidly. It was retrospective and single-center, the number of cases was small, parental testing was not systematically performed, and developmental outcomes relied mainly on telephone interviews and parental reports rather than standardized assessments for every child. For the terminated pregnancies, no systematic fetal autopsy or additional genetic testing was carried out, so other causes of the severe ultrasound findings cannot be excluded. Even so, the results align with recent prenatal series from other Chinese centers, which similarly found that most live-born children with the duplication showed no major abnormalities in early follow-up while a minority experienced neurodevelopmental or cardiac problems. Taken together, the evidence supports treating 16p13.11 microduplication as a finding to be understood, monitored, and discussed honestly, not feared automatically, and it underscores how much modern prenatal genetics still depends on long-term follow-up to turn raw copy number calls into meaningful guidance for families.

Subject of Research: Prenatal detection and postnatal outcomes of 16p13.11 microduplication identified by chromosomal microarray in a large pregnancy cohort

Article Title: Prenatal Diagnosis and Postnatal Follow‐Up of 19 Fetuses With 16p13.11 Microduplication in a Cohort of 12,038 Pregnancies From South Zhejiang

Article References: Lv, X., Li, S., Zhou, L., Wang, R., Yu, Y., Xu, C., Xu, X., Tang, X., & Li, H. (2026). Prenatal Diagnosis and Postnatal Follow‐Up of 19 Fetuses With 16p13.11 Microduplication in a Cohort of 12,038 Pregnancies From South Zhejiang. Molecular Genetics & Genomic Medicine, 14(10), Article e70324. https://doi.org/10.1002/mgg3.70324

Image Credits: AI Generated

DOI: 10.1002/mgg3.70324

Keywords: 16p13.11 microduplication, chromosomal microarray analysis, copy number variant, prenatal diagnosis, incomplete penetrance, genetic counseling, developmental delay, ventricular septal defect, low-copy repeats, NDE1, amniocentesis, genotype-phenotype correlation