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Chromosomal abnormalities detected by karyotyping and chromosomal microarray analysis in twins with structural anomalies

Lin Li, Zhiming He, Xuan Huang, Shaobin Lin, Jianzhu Wu, Linhuan Huang, Ye Wang, Qun Fang
Ultrasound in Obstetrics & Gynecology 2019 April 11

OBJECTIVE: To evaluate the incidence and types of chromosomal abnormalities in twins with structural anomalies and compare the characteristics among twins with different chorionicities and amnionicities. The added value of chromosomal microarray analysis (CMA) over conventional karyotyping in these twins was also estimated.

METHOD: A single-center, retrospective analysis was performed over an eleven-year period on 534 twin pregnancies in which one or both fetuses had congenital structural anomalies. The ultrasound findings and invasive prenatal diagnostic results were reviewed. Twin pregnancies were categorized as monochorionic monoamniotic (MCMA), monochorionic diamniotic (MCDA) or dichorionic diamniotic (DCDA). Chromosomal abnormalities detected by G-banding karyotyping or/and CMA were analyzed by chorionicity and amnionicity and by structural anomaly type.

RESULTS: Five hundred forty-nine fetuses were affected by structural anomalies in the 534 twin pairs. Of the 549 structurally abnormal fetuses, 432 (78.7%) underwent invasive prenatal testing, and cytogenetic results were obtained. The rate of overall chromosomal abnormalities in the DCDA fetuses (25.4%) was higher than that in the MCMA (3.7%) and MCDA (15.3%) fetuses. The incidence of chromosomal abnormalities detected in fetuses with anomalies of the cardiovascular, faciocervical, musculoskeletal, genitourinary and gastrointestinal systems was higher in the DCDA group than in the MCDA group. In both the DCDA and MCDA groups, hydrops fetalis was associated with the highest chromosomal abnormality rates; of these fetuses, 67.6% had Turner syndrome (45, X). Pathogenic copy number variations (CNVs) undetectable on karyotyping were found in 5 fetuses (2.0%; 95% CI, 0.3-3.7%) via CMA.

CONCLUSION: Dichorionic twins with structural anomalies have a higher risk of chromosomal abnormalities, especially aneuploidies, than do monochorionic twins. The incremental diagnostic yield of CMA over karyotyping in these twins seems lower (2.0%) than that reported in singletons. This article is protected by copyright. All rights reserved.


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