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Poster Session 1

(223) From routine to remarkable: When carrier screening incidentally reveals a chromosomal abnormality

Thursday, January 30, 2025
10:30 AM – 12:30 PM  

    Submitting Author and Presenting Author(s)

  • Jaleesa Garner, BS, MS (she/her/hers)

    Medical Student
    Michigan State University College of Human Medicine
    Flint, Michigan, United States

    • Coauthor(s)

  • EL

    Eneka Lamb, BS, MS

    Medical Student
    Michigan State University College of Human Medicine
    Grand Rapids, Michigan, United States

  • VR

    Vivian C. Romero, MD

    Michigan State University College of Human Medicine/Corewell Health Hospital
    Corewell Health Hospital /Grand Rapids, Michigan, United States

  • MC

    Marcos Cordoba, MD, MS

    Michigan State University College of Human Medicine/Corewell Health Hospital
    Corewell Health Hospital/ Grand Rapids, Michigan, United States

  • MT

    Mili Thakur, MD

    Michigan State University College of Human Medicine/Corewell Health Hospital
    Corewell Health Hospital /Grand Rapids, Michigan, United States

Objective: Routine preconception care includes expanded carrier screening. We report a case of incidental detection of an unbalanced chromosomal X-autosome translocation after carrier screening identified a sizable deletion.

Study Design: A 22-year-old nulliparous woman underwent preconception expanded carrier screening by the 436 gene panel by gene sequencing with deletion and duplication analysis.

Results: Testing detected a heterozygous 15.6 Mb deletion of the q-arm of X chromosome spanning 10 panel genes (ABCD1, AFF2, EMD, F8, FMR1, G6PD, IDS, L1CAM, MTM1, SLC6A8) in the submitted sample. Genetic counseling and further cytogenic studies, including chromosomal microarray and karyotype analysis, revealed one normal X chromosome and one X chromosome with a 15.73 MB terminal deletion of Xq27.1- >q28 and a 2.03 MB terminal duplication of 3p26.3- >p26.3. This abnormality results in monosomy for part of the X chromosome long arm (Xq27.1- >qter) and trisomy for part of the short arm of chromosome 3 (3p26.3- >ter); involving multiple OMIM genes (most proximal SOX3) and genes (CHL1 and CNTN6), respectively. There is a 50% chance of passing this unbalanced X-autosome translocation offspring. Due to the sizable X chromosome deletion, this translocation is expected to be lethal in male offspring. Female offspring who inherit it may exhibit variable phenotypic manifestations, including intellectual disability, developmental delay, and distinct facial features, depending on the ratio of X-inactivation. The patient has no health concerns and plans to proceed with in vitro fertilization (IVF) with preimplantation genetic testing for structural rearrangement (PGT-SR) for conception.

Conclusion:

Expanded carrier screening through gene sequencing can detect chromosomal translocations by identifying deletions on chromosomes. Comprehensive genetic evaluation, counseling, and further testing are crucial to understand these findings. Regardless of PGT, IVF patients should receive counseling on prenatal genetic screening and diagnostic testing for chromosomal disorders and undergo a detailed anatomy ultrasound during pregnancy.