Prenatal Chromosomal Array CGH Test

To determine the risk for the fetus being born with certain Genetic (chromosomal) abnormalities.
Patients at high-risk in biochemical maternal screen markers, patients with abnormal foetal USG findings can be offered array CGH.
This technique is not limited by tissue culture failure which affects traditional techniques like karyotyping

This test is conducted for the following reasons:

1. It estimates the likelihood that the fetus will have specific genetic (chromosomal) abnormalities.
2. Array CGH test is recommended for patients with aberrant fetal ultrasonography findings and at high risk for biochemical prenatal screen markers.

This method is not constrained by tissue culture failure, which compromises more established methods like karyotyping.

Prenatal testing should be made available to all women, along with the choice of invasive procedures. It should be done for any pregnancy for which conventional karyotyping would be recommended. Chromosomal microarray testing (aCGH) must be taken into consideration if the woman feels that her risk is high enough to warrant invasive testing.

Common considerations include:

• Older maternal age.
• Aberrant screening test results indicate a higher risk for a chromosomal disorder.
• Previous babies or pregnancies with a documented chromosomal abnormality.
• Unexpected ultrasound findings.
• Prior miscarriages or stillbirths.

cgh chromosome array test detects chromosomal aneuploidy, large chromosomal change, sub microscopic abnormalities, copy number variation (CNV)

This test measures the following markers:

1. Chromosome aneuploidy.
2. Significant chromosomal changes.
3. Submicroscopic abnormalities.
4. Copy number variation.

Your doctor will guide you on sample collection. Possible samples are amniotic fluid (20 mL), 20 mg of chorionic villus sample, prenatal cord blood in EDTA, Maternal blood sample in EDTA is mandatory. Samples should be refrigerated at 2-8 ?C but not frozen. Form G is mandatory for carrying out prenatal genetic test

Maternal blood in EDTA is also required. Samples must be kept chilled, but not frozen, at 2--8°C. Form G must be completed to do a prenatal genetic test.

CGH can detect aneuploidies like Trisomy's, large deletions & copy number variants. Patients must consult their doctor/ genetic counsellor to understand the significance of the reported findings.
This technique will not detect balanced chromosome rearrangements (which do not result in deletion or duplication of genetic material) and low level mosaicism

All women should have access to prenatal testing. Women must also be given the option of invasive procedures. aCGH should be considered for any pregnancy in which standard karyotyping would be advised if the woman feels her risk is high enough to call for invasive testing.

aCGH should be taken into consideration for any pregnancy for which routine karyotyping is available. However, many medical professionals and genetic counselors also regularly consider using an array of CGH technology for pregnancies in which an anomaly is seen by ultrasound evaluation

The doctor will guide the patient regarding the steps of the test.

Most additional or missing chromosomes can be found by employing both a karyotype and a chromosomal microarray test.

Recent investigations have determined that there is a 1% chance of having a chromosome with an additional or missing section. This risk is not age-related. A karyotype can pick up some of these alterations. However, the majority are too tiny to be observed using a microscope. Most excess or missing chromosome segments can be found using the aCGH test.

Prenatal Array CGH

Array-comparative genomic hybridization

a-CGH