Prenatal Microarray

Clinical Information

Prenatal microarray may be indicated if an abnormal maternal screening result (ex. NIPS or MSS) has been received during pregnancy or if structural anomalies are identified on ultrasound. A prenatal microarray may also be chosen if the fetus is at risk of inheriting a known familial deletion or duplication.

Technical Information

Isolated DNA is analyzed using the Illumina Diversity Array + cytogenetic (GDA+Cyto) Microarray system. This diagnostic assay identifies genomic copy number variations and loss of heterozygosity regions. VIA software (BioNano Genomics) is utilized in data analysis. SNP genotyping on this platform has the enhanced ability to identify long contiguous stretches of homozygosity (LCSH) and uniparental disomy; however, this assay cannot detect polyploidy, balanced rearrangements, point mutations, and most mosaic conditions.

All copy number changes are determined using the human genome build 38 (hg38/GRCh38). Copy number variants are reported according to the most recent International System for Human Cytogenetic Nomenclature (ISCN) guidelines. CNV classification is based on the guidelines recommended by the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resources (ClinGen). Reportable variants include pathogenic variants, likely pathogenic variants, and variants of uncertain significance. Likely benign and benign variants are not routinely reported.

Specimen Requirements

This test can be performed from direct amniotic fluid or on cultured amniocytes as well as chorionic villus sample (CVS). If sending direct fluid for microarray only, 10-20 ml of amniotic fluid is requested. Chromosomes and FISH will require an additional 10-15 ml of fluid. If sending cultured flasks, 2x T25 confluent flasks are required.

Parental samples are recommended to accompany the prenatal specimen. 3-4 ml of peripheral blood should be collected on each parent in an EDTA (lavender top) tube. Additional accepted sample types include saliva or extracted DNA.
Send approximately 5µg of extracted DNA at a requested concentration of 90-130 ng/µl.
Saliva samples must be submitted in an approved saliva kit.
Blood and saliva kits are available by request.

Transport Instructions

Amniotic fluid should be kept at room temperature; do not freeze. Specimen should be sent by courier or overnight mail to arrive at the laboratory the next day.
Blood specimens should be kept at room temperature and delivered via overnight shipping. If shipment is delayed by one or two days, the specimen should be refrigerated and shipped at room temperature. Do not freeze the specimen. Samples collected on Friday can be safely designated for Monday delivery.
Saliva is stable at room temperature and can be delivered via overnight or ground shipping.