ABSTRACT
Objective:To explore the genetic background in monochorionic diamniotic (MCDA) twins discordant for karyotypes.Methods:This study retrospectively analyzed four pregnant women who were diagnosed as having MCDA twins with prenatal diagnostic indications by ultrasound at Maternity and Child Health Care of Guangxi Zhuang Autonomous Region from January 2016 to December 2019. Dual amniocentesis was performed for all cases guided by ultrasound and the twin amniotic fluids were taken for karyotyping and single nucleotide polymorphism (SNP) array testing. Zygosity was determined by SNP genotype analysis.Results:The karyotypes of four MCDA twins were 47,XX,+18 and 46,XX, 45,X and 46,XX, 47,XXY[17]/46,XY[33] and 47,XXY, and 47,XX,+21 and 46,XX, respectively. The results of SNP were arr(18)×3 and arr(1-22,X)×2, arr(X)×1 and arr(1-22,X)×2, arr(X)×1~2,(Y)×1 and arr(X)×2,(Y)×1, arr(21)×3 and arr(21)×2~3. All of them were monozygotic twins according to the SNP genotypes. Three out of the four cases chose to terminate the pregnancy due to fetal chromosomal abnormalities and one was lost to follow-up. One gave birth to a healthy child in the next pregnancy.Conclusions:Clinicians should be alert to the discordant karyotypes in MCDA twins, of which the mechanism is yet to be explored.