Dr. Kimberly Martin

California

Title: Genetic Screening using cell-free DNA Changes Obstetrical Care

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Biography

Abstract

Abstract:  

Prenatal genetic screening and diagnosis has traditionally focused on Down syndrome (Trisomy 21) and been primarily offered or encouraged for older women however the availability of cell-free DNA (cfDNA) as a highly sensitive and specific non-invasive screen requires a reevaluation of what genetic conditions are included in screening, and who screening is offered to.   The superior performance of cfDNA for common autosomal and sex chromosome abnormalities is established in singleton pregnancies for all women, compared to serum analyte and ultrasound markers.  Use of a blood draw in the primary healthcare provider’s office streamlines the screening process and increases access.  Sex chromosome trisomies screening was not possible before implementation of cfDNA, and screening performance has been validated. The increasing number of effective early interventions to improve outcomes for affected individuals suggests that incorporation of the sex chromosomes is appropriate. 

Use of cfDNA has been shown to be a significantly more effective aneuploidy screenfor twins.  The use of a single nucleotide polymorphism (SNP)c-based cfDNA test provides the first non-invasive means of determining twin zygosity.   Highly effective aneuploidy screening for twin pregnancies has not been available previously, and the addition of zygosity assessment can refine the counseling when assignment of chorionicity is unreliable, and when twins are discordant for ultrasound abnormalities.

Despite the increasing use of chromosomal microarray for prenatal diagnostic testing, the inclusion of the 22q11.2 deletion syndrome in cfDNA screening has not become common practice.  The performance of cfDNA for 22q11.2 deletion syndrome screening has recently been established an international, large unselected obstetrical population.  New data suggest that inclusion of 22q11.2 deletion syndrome in prenatal screening impacts obstetrical care. 

Women who request screening for common genetic conditions should be offered cfDNA as the first approach. It’s use in twin pregnancies has been validated, and the inclusion of zygosity broadens the clinical applications.  The 22q11.2 deletion syndrome meets the criteria for population-based screening, and cfDNA is a validated, effective tool.