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Rate of prenatal diagnostic testing among women with genetic conditions 

Prenatal Genetics
  • Primary Categories:
    • Prenatal Genetics
  • Secondary Categories:
    • Prenatal Genetics
Introduction:
Prenatal diagnostic genetic testing allows for early identification of significant conditions in the fetus and enables informed decision-making about available options or potential actions. While studies demonstrate a decline in the uptake of prenatal diagnostic testing following the implementation of cell-free DNA based screening, this screening is generally not aimed at detecting small copy number variations or single gene disorders This is particularly pertinent for women with known familial genetic disorders due to the elevated risk of transmission of these conditions to their offspring. This study aimed to assess the rate of prenatal diagnostic testing among women with genetic conditions.

Methods:
We conducted a retrospective analysis of maternal and fetal outcomes in pregnancies among patients with genetic disorders, identified via molecular diagnosis or clinical criteria, who delivered at a single institution across two delivery sites between 2013 and 2024.  Only the first recorded delivery within our healthcare system was included in this analysis. The primary outcome measures were the rate of prenatal diagnostic testing and the rate of positive findings. Non-parametric statistical methods were used to evaluate the data. 

Results:
We reviewed the records of 106 patients with genetic disorders. We excluded three patients due to missing information. The genetic disorders represented include chromosomal (18, most commonly mosaic Turner syndrome), renal (18), inborn errors of metabolism (16), connective tissue (100), skeletal (9), multi-system disorders (8), neurocutaneous (6), endocrine (6), RASopathies (4), neuromuscular (3), albinism (3), vascular (3), hematologic (1), and oncologic (1). The most common mode of inheritance of the maternal disorder was autosomal dominant (60/106; 57%), followed by autosomal recessive (21/106; 20%), unknown (14/106; 13%), and X-linked (11/106; 10%). Prenatal diagnostic genetic testing was conducted for 14/106 patients (13%). Of the patients that underwent prenatal diagnostic testing, 7/14 (50%) inherited a maternal single nucleotide variant or chromosomal rearrangement. One fetus had a de novo chromosomal rearrangement. Of the 92 patients who did not have prenatal diagnostic testing, 6 had postnatal testing, and 5 (83%) of those inherited the maternal genetic disorder.  In total, 12 of the 20 patients that underwent diagnostic testing, 7 from the prenatal diagnostic testing group and 5 from the postnatal diagnostic testing group, inherited the maternal pathogenic variant (60%).  

Conclusion:
The rate of prenatal diagnostic testing was low in this population whose offspring has an increased risk of inheriting a genetic disorder compared to the general population. Furthermore, most of the patients had autosomal dominant conditions, which confer a 50% risk of transmission to their offspring. This makes the notably low rate of prenatal diagnosis unexpectedly surprising. Prenatal diagnostic testing in women with genetic disorders has significant implications for perinatal planning. Early detection of significant fetal conditions supports informed decision-making regarding available management options. The ability to proactively pursue diagnostic testing, potential treatments, preparation for neonatal care, or termination of the pregnancy is dependent on access to prenatal diagnosis. Further studies are needed to evaluate barriers to diagnostic testing in this population.

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