Clinician-reported chorionicity and zygosity assignment using single-nucleotide polymorphism-based cell-free DNA:...

Area of Science:

• Reproductive Medicine
• Genetics
• Maternal-Fetal Medicine

Background:

• Prenatal chorionicity assessment commonly uses ultrasound, but accuracy can be limited by various factors.
• Noninvasive zygosity determination is achievable through single nucleotide polymorphism (SNP)-based cell-free DNA (cfDNA) testing.

Purpose of the Study:

• To investigate the correlation between provider-reported chorionicity and zygosity assigned by SNP-cfDNA testing in twin pregnancies.

Main Methods:

• Analysis of 59,471 twin pregnancy blood samples received by a reference laboratory.
• Correlation of SNP-cfDNA zygosity results (monozygotic or dizygotic) with provider-assigned chorionicity (monochorionic, dichorionic, or unknown).

Main Results:

• Out of 55,344 samples with zygosity assignment, 30.1% were monozygotic (MZ) and 69.9% were dizygotic (DZ).
• Among 6,283 provider-reported monochorionic (MC) twins, 5.1% were discordant, identified as DZ by SNP-cfDNA.
• One in 20 suspected MC twin pregnancies were found to be DZ via SNP-cfDNA testing.

Conclusions:

• SNP-cfDNA zygosity assessment serves as a valuable adjunct in twin pregnancy evaluation.
• This method is especially beneficial for twin pregnancies reported as monochorionic or those with undetermined chorionicity.