What is Prenatal Trio Whole Exome Sequencing?
The Prenatal Trio Whole Exome Sequencing (WES) is a powerful test for when prenatal imaging detects an anomaly consistent with an underlying genetic etiology. Prenatal Trio WES is often considered after fetal chromosome microarray analysis has not been diagnostic.
In contrast to single gene or panel sequencing tests that analyze one gene or small groups of related genes at a time, the Prenatal Trio WES test will analyze the exons (coding regions) of thousands of genes simultaneously using next-generation sequencing techniques.
The exome refers to the portion of the human genome that contains functionally important sequences of DNA that direct the body to make proteins essential for the body to function properly. These regions of DNA are referred to as exons. There are approximately 180,000 exons in the human genome which represents about 3% of the genome. These 180,000 exons are arranged in approximately 22,000 genes. Most errors that occur in DNA sequences causing genetic disorders are in the exons. Sequencing of the exome is thought to be an efficient method of analyzing a patient's DNA to discover the genetic cause of diseases or disabilities.
This test sequences the exome nucleotide by nucleotide, to a depth of coverage necessary to build a consensus sequence with high accuracy. This consensus sequence is then compared to normal population standards and references, and the result is interpreted by board-certified laboratory directors and clinicians. By sequencing the exome of a patient and comparing it to normal reference sequence, variations in an individual's DNA sequence are identified and associated with medical conditions.
The fetal report includes pathogenic or likely pathogenic variants in disease genes related to the prenatal indications. Variants in disease genes unrelated to the prenatal indications but likely to cause significant disorders during childhood.
Indications for Testing
• Prenatal ultrasound with abnormal findings
• Positive prenatal screening tests
• Uninformative prior prenatal diagnostic testing
• A previous child, family history, or pregnancy loss with possible genetic disease
Special Note
Fetal report includes:
Pathogenic or likely pathogenic variants in disease genes related to the prenatal indications. Variants in disease genes unrelated to the prenatal indications but likely to cause significant disorders during childhood.
Parental reports include:
Pathogenic variants in genes included in the ACMG policy statement regarding recommendations for reporting of incidental findings will be reported as medically actionable.
Limitations
The interpretation of nucleotide changes is based on our current understanding of the specific genes. This interpretation may change over time as more information about these genes becomes available. Possible diagnostic errors include sample mix-ups, genetic variants that interfere with analysis, incorrect assignment of biological parentage, or other sources. Please contact a genetic counselor at Baylor Genetics if there is reason to suspect one of these sources of error.
14 days
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