A chromosome blood test is a type of NIPT (Non-Invasive Prenatal Testing) genetic screening method used for identifying and analyzing the presence of chromosomal abnormality in the fetus. As a part of genetic screening, it diagnoses the predisposition of certain genetic disorders during the fetal stage.
The non-invasive technique draws a small amount of maternal blood and extracts cell-free (cfDNA) DNA from a baby circulating in the mother’s blood. The cfDNA is analyzed for markers to screen for the presence of a genetic condition. It is most commonly used for screening for Down Syndrome.
Who Should Take the Chromosome Blood Test?
The Chromosome Blood Test is recommended for every pregnant woman during their first and second trimester. The prenatal screening test helps in identifying the presence of aneuploidy or other chromosomal aberrations in the fetus.
The prenatal Chromosome Blood Test is readily available at an affordable price at the best NIPT tests labs. It is highly recommended for pregnant women above the age of 35 years or older couples. A gynaecologist often recommends chromosome blood tests for genetic screening to be on the safer side. However, it does not mean there is something wrong. It is simply a great precautionary measure.
In case, there is a genetic disorder or chromosomal aberration detected during the test, the decision is up to the family or expecting mother. If there is a family history of genetic disorders, it is highly recommended to take the chromosomal blood test for diagnosing the presence or absence of genetic abnormalities before birth.
What Conditions can Chromosome Blood Test Detect?
Many genetic disorders can be detected by undertaking chromosome blood tests. Here are examples of some of the genetic disorders that can be diagnosed by taking the prenatal genetic screening.
- Down Syndrome (Trisomy 21)
- Cystic Fibrosis
- Polycystic Kidney Disease
- Sickle Cell Anemia
- Duchenne Muscular Dystrophy
- Thalassemia
- Tay Sachs Disease
- Edwards Syndrome (Trisomy 18)
- Patau Syndrome (Trisomy 13)
- Klinefelter Syndrome
- Turner Syndrome
However, the genetic disorder is not only limited to this list.
How does the Test Work for Genetic Screening?
The chromosome blood test during pregnancy can be done in the best genetic screening lab in India for accurate diagnosis. The screening is done during the first and second trimesters. During the first trimester, the blood test is conducted by drawing blood between 9 to 13 weeks of pregnancy. An abnormal measurement in the chromosome indicates a fetus with the potential risk of Down Syndrome (Trisomy 21) or Edwards or Patau Syndrome. The quadruple screen is a chromosome blood test conducted during the second trimester between 15 and 21 weeks of pregnancy to diagnose the risk of a genetic disorder.
The cfDNA analysis is the blood test used for prenatal genetic screening. In individuals with high risk, the test can provide up to 99% of accurate results in the affected pregnancies. The test counts the cfDNA in the mother’s blood and examines the chromosome to find if there is an extra copy or deletion of a copy from any of the chromosomes.
Do Positive Results for Genetic Screening Indicate 100% Genetic Disorder?
The prenatal genetic screening analyzes any abnormality in the chromosome and identifies the potential risk of a genetic disorder in the fetus. It is simply a screening test and does not 100% mean that the baby will be born with a genetic disorder. The confirmation would further require the diagnostic test to accurately provide information on the genetic status of the baby.
What is the Best Time to Take Chromosome Blood Test?
The best labs in India recommend taking a chromosome blood test during the first trimester, as early as the 10th week of pregnancy. The decision should be made early to avoid any complications. In case the test report comes as positive, the growing fetus has a chance of a chromosomal disorder. The further course of action will be discussed by a genetic counsellor. Further, diagnostic tests like chorionic villus sampling or amniocentesis would help in the accurate screening of the presence or absence of genetic issues.
