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Updated: Feb 12, 2026

Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing
Published on: February 10, 2023
Unusual twinning: Additional findings during prenatal diagnosis of twin zygosity by single nucleotide polymorphism
Zhiyong Zou1, Linhuan Huang1, Shaobin Lin1
1Department of Obstetrics & Gynecology, The First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, China.
Objective:
To evaluate the incidence and characteristics of unusual twinning by using single nucleotide polymorphism (SNP) array to identify twin zygosity.
Methods:
This study reviewed 386 twin pairs who were seen for prenatal or postnatal diagnosis and underwent SNP array to detect zygosity.
Results:
The incidence of monozygotic (MZ) twins was 11.36% (25/220) in the assisted reproductive technology (ART)-conceived group. Monochorionic dizygotic twins represented 3 of 24 monochorionic ART-conceived twin pairs (3/24, 12.50%) but none in the spontaneous twin pairs. Among 4 single-embryo transfer twin pairs, 3 represented unusual twinning, including 2 MZ twin pairs with discordant karyotypes and 1 dizygotic twin pair of the same gender. Of the pregnancies with 2 or more embryos transferred, 7.77% (15/193) were MZ. Additionally, there was a dichorionic monozygotic twin pair with placental vascular anastomoses from a day-5 blastocyst transfer.
Conclusion:
Single nucleotide polymorphism array can provide zygosity diagnosis in addition to chromosomal copy number variation and uniparental disomy detection. ART twin pregnancies have a risk of unusual twinning, such as monochorionic dizygotic, single-embryo transfer twin pairs with discordant karyotypes or dizygotic, and dichorionic monozygotic with vascular anastomoses from day-5 transfer.
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