25429 Chromosomal Microarray Prenatal, Amniotic fluid/Chorionic Villus Sampling (CMAP)

​​Oligonucleotide Array, Oligo Array, Single Nucleotide Polymorphism (SNP) Array, Whole Genome Array, Molecular Karyotype, Constitutional Array, Prenatal Diagnosis, aCGH, array CGH, Array Comparative Genomic Hybridization, Amniotic fluid, Chorionic villi sample or CVS​, CytoScan, Microarray, Accel

AF CMAPDSO

​Additional Testing Requirements:

A maternal blood sample is requested when ordering this test (see PPAP / Parental Sample Prep for Prenatal Microarray Testing); the PPAP test must be ordered under a different order number than the prenatal specimen.

A paternal blood sample is desired but not required (see PPAP / Parental Sample Prep for Prenatal Microarray Testing).

Portions of the specimen may be used for other tests such as measuring markers for neural tube defects (eg, AFPA / Alpha-Fetoprotein, Amniotic Fluid), molecular genetic testing, biochemical testing, and chromosome and FISH testing (including CHRAF / Chromosome Analysis, Amniotic Fluid; CHRCV / Chromosome Analysis, Chorionic Villus Sampling; and PADF / Prenatal Aneuploidy Detection, FISH).

If additional molecular genetic or biochemical genetic testing is needed, order CULAF / Culture for Genetic Testing, Amniotic Fluid or CULFB / Fibroblast Culture for Genetic Testing so that cultures may be set up specifically for use in these tests.

Prenatal diagnosis of copy number changes (gains or losses) across the entire genome.

Determining the size, precise breakpoints, gene content, and any unappreciated complexity of abnormalities detected by other methods such as conventional chromosome and fluorescence in situ hybridization studies.

Determining if apparently balanced abnormalities identified by previous conventional chromosome studies have cryptic imbalances, since a proportion of such rearrangements that appear balanced at the resolution of a chromosome study are actually unbalanced when analyzed by higher-resolution chromosomal microarray

Assessing regions of homozygosity related to uniparental disomy or identity by descent

*NOTE:  Testing requires special order supply item T095 for collection and transport of Chorionic Villi Specimens (CVS).  Please contact Marshfield Campus Lab-Supportive Services department (715-221-​6220) at least one week prior to sample collection to special order the required collection container supply item for CVS specimens. 

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​A reason for testing must be submitted with each sample.  The laboratory will not reject testing if this information is not provided, but appropriate testing and interpretation may be compromised or delayed.  Notify the laboratory if the pregnancy involves an egg donor or gestational carrier. 

Amniotic Fluid
1. Optimal timing for specimen collection is during 14 to 18 weeks of gestation, but specimens collected at other weeks of gestation are also accepted. Provide gestational age at the time of amniocentesis.

2. Discard the first 2 mL of amniotic fluid.

3. Place the tubes in a Refrigerate/Ambient Shipping Box, 5 lb.

4. Fill remaining space with packing material.

Chorionic Villi
1. Collect specimen by the transabdominal or transcervical method.
2. Transfer chorionic villi to a Petri dish containing CVS (RPMI) transport medium.
3. Using a stereomicroscope and sterile forceps, assess the quality and quantity of the villi and remove any blood clots and maternal decidua.

​All specimens will be evaluated at Mayo Clinic Laboratories for test suitability. 

This test does not detect all types and instances of uniparental disomy.

This test is not designed to detect low-level mosaicism, although it can be detected in some cases.

This test does not detect point alterations, small deletions or insertions below the resolution of this assay, or other types of variants such as epigenetic changes.

The results of this test may reveal incidental findings not related to the original reason for referral. In such cases, studies of additional family members may be required to help interpret the results.

​Chromosomal abnormalities cause a wide range of disorders associated with birth defects and intellectual disability. Many of these disorders can be diagnosed prenatally by analysis of chorionic villi or amniocytes.

The most common reasons for performing cytogenetic studies for prenatal diagnosis include advanced maternal age, abnormal prenatal screen, a previous child with a chromosome abnormality, abnormal fetal ultrasound, or a family history of a chromosome abnormality. Chromosomal microarray (CMA) is a high-resolution method for detecting copy number changes (gains or losses) across the entire genome in a single assay and is sometimes called a molecular karyotype. The American College of Obstetricians and Gynecologists and the Society for Maternal-Fetal Medicine recommend the chromosomal microarray as a replacement for the fetal karyotype in patients with a pregnancy demonstrating one or more major structural abnormalities on ultrasound when undergoing invasive prenatal diagnosis.(1)

This CMA test utilizes greater than 2 million copy number probes and approximately 750,000 single nucleotide polymorphism probes for the detection of copy number changes and regions with absence of heterozygosity. Identification of regions of excessive homozygosity on a single chromosome could suggest uniparental disomy, which may warrant further clinical investigation when observed on chromosomes with known imprinting disorders. In addition, the detection of excessive homozygosity on multiple chromosomes may suggest consanguinity.

An interpretive report will be provided.​