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What Is Fetal Chromosomal Aneuploidy Test?

What Is Fetal Chromosomal Aneuploidy Test?

Fetal chromosomal aneuploidy testing analyzes a developing baby's chromosomes to identify any abnormal numbers. Chromosomes are the thread-like structures within cells that carry our genetic information. Normally, humans have 46 chromosomes, 23 inherited from each parent. However, sometimes an error occurs during cell division, resulting in an abnormal number of chromosomes in the fetus. This is called fetal chromosomal aneuploidy.

There are two main types of fetal chromosomal aneuploidy:

  • Trisomy: This occurs when a baby has three copies of a particular chromosome instead of the usual two. The most common trisomies are Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13).

  • Monosomy: This occurs when a baby has only one copy of a chromosome instead of two. Monosomy is less common than trisomy and is often incompatible with life.

Fetal chromosomal aneuploidy tests are not mandatory but are offered to pregnant women, especially those considered at higher risk.

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Who Might Consider Fetal Chromosomal Aneuploidy Testing?

Several factors can increase a woman's chance of having a baby with a chromosomal abnormality. These include:

  • Advanced maternal age: The risk of having a baby with Down syndrome increases with a woman's age, particularly after 35.

  • Previous pregnancy with a chromosomal abnormality: If a couple has already had a child with a chromosomal abnormality, they have a higher risk of having another affected child.

  • Family history of chromosomal abnormalities: If there is a family history of chromosomal abnormalities on either side, the risk may be slightly increased.

  • Abnormal prenatal screening test results: Certain prenatal screening tests, such as the combined first-trimester screening or the quad screen, can indicate an increased risk of chromosomal abnormalities. However, these tests are not diagnostic.

Types of Fetal Chromosomal Aneuploidy Tests

There are two main categories of fetal chrmoml aneuploidy tests:

1. Screening Tests:

  • Combined first-trimester screening: This combines a blood test with an ultrasound measurement of the nuchal translucency (fluid collection at the back of the baby's neck) to estimate the risk of Down syndrome, Edwards syndrome, and Patau syndrome.

  • Quad screen: This blood test measures four substances in the mother's blood (alpha-fetoprotein, human chorionic gonadotropin, estriol, and inhibin-A) to estimate the risk of Down syndrome, Edwards syndrome, and spina bifida.

  • Cell-free fetal DNA (cffDNA) testing: This non-invasive prenatal test (NIPT) analyzes fetal DNA fragments circulating in the mother's blood to estimate the risk of Down syndrome, Edwards syndrome, Patau syndrome, and sometimes sex chromosome aneuploidies.

2. Diagnostic Tests:

  • Chorionic villus sampling (CVS): This test involves taking a small sample of tissue from the placenta, which shares the baby's genetic makeup. CVS is usually performed between 10 and 13 weeks of pregnancy.

  • Amniocentesis: This test involves withdrawing a small amount of amniotic fluid, which surrounds the baby, for analysis. Amniocentesis is typically performed between 15 and 20 weeks of pregnancy.

Important Note: Screening tests are not diagnostic and only indicate an increased risk. Diagnostic tests provide a definitive answer about the baby's chromosomes. However, they are also invasive procedures that carry a small risk of miscarriage.

Cost of Fetal Chromosomal Aneuploidy Testing (3x)

The cost of fetal chromosomal aneuploidy testing (3x) varies depending on the type of test, insurance coverage, and location.

  • Screening tests: These are typically covered by most insurance plans.

  • Cell-free fetal DNA testing (cffDNA): Costs for cffDNA testing (3x) can range from $1,000 to $3,000, with some insurance plans offering partial or full coverage.

  • Diagnostic tests: Diagnostic tests like CVS and amniocentesis are usually covered by insurance if a woman has an increased risk of having a baby with a chromosomal abnormality. However, some out-of-pocket costs may still apply.

Conclusion of Fetal Chromosomal Aneuploidy Test

Fetal chromosomal aneuploidy testing can provide valuable information to expectant parents. Understanding the risks and benefits of these tests can help couples make informed decisions about their pregnancy. It is crucial to discuss testing options with a healthcare provider to determine if testing is right for you and which type of test may be most appropriate.

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