Chromosome testing during pregnancy is a type of genetic testing that looks at the chromosomes in a developing baby to check for any abnormalities. Chromosomes are structures in the body’s cells that carry genetic material. There are usually 46 chromosomes in each cell, and they are arranged in 23 pairs. Abnormalities in the number or structure of chromosomes can cause genetic conditions.
There are several types of chromosome testing that can be done during pregnancy, including:
- Chorionic villus sampling (CVS): This test is usually done between 10 and 13 weeks of pregnancy. A small sample of tissue called the chorionic villi is taken from the placenta and tested for chromosomal abnormalities.
- Amniocentesis: This test is usually done between 15 and 20 weeks of pregnancy. A small sample of amniotic fluid, which surrounds the developing baby, is taken and tested for chromosomal abnormalities.
- Non-invasive prenatal testing (NIPT): This test can be done as early as 10 weeks into pregnancy. It involves analyzing a sample of the pregnant woman’s blood to look for the baby’s DNA. NIPT can screen for certain chromosomal abnormalities, such as Down syndrome, but it cannot diagnose all chromosomal conditions.
Chromosome testing during pregnancy can be helpful for people who are at an increased risk of having a baby with a chromosomal abnormality. It is important to understand that chromosome testing is optional and the decision to have it is a personal one. It is a good idea to discuss the risks and benefits of chromosome testing with your healthcare provider and a genetic counselor before making a decision.
Prenatal testing: Is it right for you?
Diagnostic tests. If a screening test indicates a possible problem — or your age, family history or medical history puts you at increased risk of having a baby with a genetic problem — you might consider an invasive prenatal diagnostic test. A diagnostic test is the only way to be sure of a diagnosis. Some diagnostic tests, such as chorionic villus sampling and amniocentesis, carry a slight risk of miscarriage.
How Is Genetic Testing Done?
Genetic tests can be done on small samples of blood or saliva (spit). In pregnant women, genetic testing can be done on amniotic fluid (through amniocentesis) or the placenta (through chorionic villus sampling). Testing can also be done on an embryo during in vitro fertilization (IVF). Usually, it takes a few weeks for test results to be ready.
What Can Genetic Testing Find?
Depending on the test, doctors can find if someone has an illness, is at risk for an illness, and/or is a carrier for an illness. A carrier doesn’t have the illness but can pass the gene change to their children.
Genetic testing usually can be done if the genetic changes for an illness are known. For example, testing can be done for:
- Cystic fibrosis
- Tay-Sachs disease
- Sickle cell disease
- Down syndrome
- Spina bifida
- Turner syndrome
- Von Willebrand Disease
- Albinism
- Duchenne muscular dystrophy
In some cases, it also can show how a person will respond to certain medicines, or if they are more likely to get some types of cancer.
