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Prenatal Diagnosis with Chromosomal Microarray Analysis

Guideline Watch |
November 21, 2013

Prenatal Diagnosis with Chromosomal Microarray Analysis

  1. Allison Bryant, MD, MPH

New guidelines recommend chromosomal microarray as a first-line genetic test in the setting of ultrasonically identified fetal structural abnormalities.

  1. Allison Bryant, MD, MPH

Sponsoring Organizations: American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine

Background and Objective

Although conventional karyotyping following chorionic villus sampling or amniocentesis has long been standard analysis, this approach cannot detect submicroscopic abnormalities such as DNA deletions and duplications. Chromosomal microarray analysis can identify these copy number variants by comparing hybridization of fetal DNA with that of DNA sequences of known identities. Recent results of a large NIH-sponsored study of karyotyping compared with chromosomal microarray analysis showed that microarray detected clinically meaningful abnormalities in 6% of fetuses with ultrasonically detected structural abnormalities but normal karyotypes and in 2% of fetuses with normal ultrasound findings and karyotypes. This study also highlighted the phenomenon of copy number variants of unknown clinical significance, which occurred in 3% of cases.

In the wake of these important findings, the American College of Obstetricians and Gynecologists and the Society for Maternal Fetal Medicine have released joint guidelines about chromosomal microarray for prenatal diagnosis.

Key Recommendations

  • In women who choose to undergo invasive prenatal diagnosis, if at least one major fetal structural anomaly has been ultrasonically diagnosed, chromosomal microarray analysis should be performed instead of fetal karyotyping.

  • In women with no fetal structural abnormalities who choose to undergo invasive prenatal diagnosis, either karyotyping or microarray analysis is appropriate.

  • Microarray analysis should not be limited to women aged ≥35.

  • If fetal demise has occurred and cytogenetic diagnosis is desired, microarray analysis is recommended.

  • Careful pre- and posttest counseling by appropriately trained personnel is required. The informed consent process must include a discussion of the possibility of copy number variants of unknown clinical significance.

Comment

Chromosomal microarray analysis can provide additional genetic detail to guide pregnancy management — however, the need for rigorous counseling of patients cannot be emphasized enough. The detection of copy number variants of unknown clinical significance can be anxiety-provoking, particularly without full data on which to provide counseling. As these data accrue in clinical practice, outcomes associated with such copy number variants can be shared broadly, moving their significance from “unknown” to “known.” Lastly, these recommendations should inform healthcare policy to ensure adequate coverage for these tests. Lowering financial barriers will help eliminate disparities in access to these novel diagnostic tools.

  • Disclosures for Allison Bryant, MD, MPH at time of publication Nothing to disclose

Citation(s):

Reader Comments (2)

Ahmed Fetouh Other Healthcare Professional, Obstetrics/Gynecology, Cairo ,Egypt

Very useful knowledge

ashok ashtekar.MD Physician, Internal Medicine, pune, india

CMA should be done even without structural abnormality on sonography.

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