Prenatal genetic tests?
Prenatal genetic examinations and diagnostic tests provide information on the fetus’s health. It can help families and health care providers make decisions about pregnancy or fetus.
Genetic tests verify congenital conditions such as Down’s syndrome, trisomy 13 and spina bifida.
What is prenatal genetic tests
Prenatal genetic tests give parents information about genetic disorders or birth abnormalities that the fetus may experience.
Unlike some routine prenatal tests such as blood type, blood count or glucose test, these tests are optional. Talk to your doctor and select the right tests for you.
Some people decide to perform prenatal genetic tests in addition to routine pregnancy testing. Prenatal genetic testing is optional.
Chromosomes or genes in a person cause genetic disorders. The gene is a part of the body’s cells that stores instructions for how your body works.
Chromosome carries your genes. Congenital disorders exist at birth, and health care providers can diagnose some of these conditions before birth.
There are two different types of tests: screening tests and diagnostic tests.
Types of prenatal genetic tests
Screening tests do not diagnose genetic conditions, and an abnormal result does not mean that the fetus has a problem or abnormality.
This means that there is a greater risk of developing a genetic disorder. A specialist doctor can help interpret the results of genetic screening tests and explain the next steps.
In some cases, they may recommend a diagnostic test.
Some prenatal genetic tests are:
carrier screening
The carrier’s examination is a blood test that the competent physician may give you.
This type of test can identify small changes in genes that increase the risk of the embryo inheriting serious medical conditions.
These conditions are often called monogene. Examples include cystic fibrosis, sickle cell disease and spinal muscle atrophy.
If a blood test shows that you are at a genetic risk, the husband must also undergo an examination.
If both parents have the same genetic risk, the foetus may have a more severe form of disease. Simply complete the carrier inspection tests once in your life.
Examination of an abnormal chromosome number
Chromosomes must be inherited in pairs-one half of a pair from a married couple.
Sometimes, a defect occurs during fertilization, which leads to the loss or increase of chromosome pair segments.
Examples include Down syndrome (extra chromosome 21) and Turner syndrome (missing X chromosome). These test results will be different for each pregnancy.
The types of tests include:
- Cell-free fetal DNA screening: this is known as non-invasive prenatal testing (NIPT). Genetic testing doctors look for some common forms of abnormal chromosome numbers in small pieces of fetal DNA that are in your blood. Since fetal DNA is present in very small quantities, doctors cannot do the test until 10 weeks of pregnancy.
- Serum test: this type of test is also performed on a blood sample. It does not look directly at the fetal DNA. Instead, these tests analyze different protein levels in the blood to determine the risk of abnormal chromosome numbers.
- Examples of this type of test include serial screening, quad screen and first trimester serum screening. Each of these tests should be performed at very specific times during pregnancy, but the doctor does not perform any of these tests until the 11th week of pregnancy.
Examination of physical abnormalities
Sometimes missing or extra chromosomes cause changes in the physical structure of your baby.
For example, the chromosomes are normal but your baby has a physical defect.
During pregnancy, ultrasound and blood tests can help determine the risk of the fetus developing physical abnormalities and assess whether they may be due to genetic abnormalities or not.
- Occipital labiaplasty: ultrasound is used to measure the thickness of the back of the fetal neck. Thick nuchal translucency gives us clues about the risk of having an abnormal chromosome number and physical abnormalities such as abnormal fetal heart formation. Doctors perform this ultrasound at the 11th to 14th week of pregnancy.
- Maternal serum test: the doctor draws blood from the mother to measure the fetal protein level. Elevated levels may indicate physical problems in the abdomen, face, or spine of the fetus. This happens at the 15th to 22nd week of pregnancy.
- Quad scan: measures the levels of four substances in the blood and determines the risk of the fetus developing chromosomal abnormalities and neural tube defects. It is performed at the 15th to 22nd week of pregnancy.
- Fetal anatomy examination: ultrasound is used to assess the physical structures of the fetus, including the development of the brain, skeleton, heart, kidneys, abdomen, face, arms and legs. This ultrasound is usually performed at 18 to 20 weeks of pregnancy.
What types of prenatal genetic tests
Prenatal genetic tests can confirm whether the fetus has a genetic condition. These tests take cells of amniotic fluid or placenta and test them for specific disorders.
Diagnostic testing is performed only when the screening test is abnormal or if you are at high risk of having a child with a genetic condition.
The most common diagnostic tests are:
- Amniotic insertion: The doctor inserts a needle into the womb to remove a sample of amniotic fluid from the amniotic cyst. Tuberculosis occurs between 16 and 20 weeks of pregnancy.
- CVS samples: The doctor inserts a needle into the uterus to remove a small sample of cells from the placenta. The doctor will determine whether placing the needle through your abdomen or vagina is safer. This occurs in 11 to 13 weeks of pregnancy.
Who should undergo a genetic test
The decision to conduct prenatal genetic tests is a personal choice. But you better ask your doctor what to recommend if you’re not sure.
The results provide important information about fetal health. Doctors offer all pregnant women genetic screening as part of pregnancy care.
Some of the reasons families choose diagnostic genetic tests during pregnancy are:
- Irregular result of genetic testing.
- Family or personal history of genetic conditions.
- Pregnancy is above the age of 35.
- Repeated abortions or stillbirths.
Who should undergo prenatal genetic testing
How is prenatal genetic testing done?
Most prenatal genetic tests use pregnant women’s blood. If the results of the screening test indicate a high risk of a congenital condition, doctors will conduct more accurate tests to diagnose certain conditions. Invasive diagnostic tests include amniocentesis and chorionic villus sampling.
Examinations that are performed in the first trimester of pregnancy
The first trimester serum is examined, cell-free fetal DNA examined and NT ultrasound examined in 11 to 14 weeks of pregnancy. Combining information from blood tests with ultrasound results indicates the high risk of some common chromosomal disorders, such as Down’s syndrome.
You can perform complete examinations at any time during pregnancy, even as early as 6 to 10 weeks of pregnancy.
These tests verify “individual gene” genetic conditions that are likely to be transmitted to the foetus. The carrier’s examination will not identify cases due to abnormal chromosome numbers, such as Down’s syndrome.
A cell-free fetal DNA (a non-invasive prenatal examination or test) examines your blood for fetal DNA.
It looks for chromosomal conditions such as Down syndrome, one third of the pigment 13 and one third of the pigment 18. Your doctor can perform this examination as early as 10 weeks of pregnancy, or later during pregnancy.
Tests performed in the second trimester of pregnancy
Second trimester examinations occur between 15 and 22 weeks of pregnancy.
Blood testing in the second trimester of pregnancy, examination of mother’s serum include alpha-vitoprotein (AFP) and quadruple screening.
A quadruple test is called because it measures four proteins: alpha-vitoprotein (AFP), estriol, gonadotropin, human placenta (HCG) and enhybin-A.
These tests can help the doctor determine whether the fetus is at increased risk of genetic or physical abnormalities.
Ultrasound for fetal anatomy is another way of examining genetic or physical abnormalities of the fetus.
When can test results be obtained
The results of genetic testing take several days. Diagnostic test results can take several days or even weeks to complete. In most cases, they are sent to the lab. Your doctor will receive the test results first, and then share the results with you.
What the results of genetic testing mean
Genetic screening tests only measure risk. They do not tell you for sure if the fetus has a genetic condition. A positive result means that the fetus is more likely to develop this disorder. A negative result means that the fetus is less likely to develop this disorder.
Your doctor may suggest diagnostic tests such as chorionic villus samples or amniocentesis. A genetic pathologist who specializes in high-risk pregnancies and genetic conditions may be consulted.
Do genetic screening tests affect the mother
No, it’s not bad for you. Diagnostic tests such as amniocentesis carry some risks. That is why diagnostic tests are performed only when doctors suspect a genetic condition and not during routine prenatal genetic examinations.
At what week of pregnancy are genetic tests performed?
It depends on the test. Most doctors perform genetic tests after 10 weeks of pregnancy and before 22 weeks of pregnancy. At this time, screening or diagnostic tests can be carried out no earlier than 10 weeks after conception.
Do genetic screening tests tell you the gender of the child
Cell-free DNA screening (NIPT) can provide information about the sex of the fetus as well as information about the risk of genetic conditions. An ultrasound may also be able to tell you about gender
What questions should I ask my doctor about genetic testing
Pregnancy tests and diagnostic tests are a personal choice. You’ll probably have questions about which screening tests you should get or what the test results mean.
Don’t be afraid to ask questions. Remember, only you and your family can determine how to handle positive results from both types of genetic testing.
There is no correct or wrong answer when it comes to prenatal genetic testing. The decision is up to you and your family.
If you are concerned about prenatal tests or need clarification about what each test is looking for, talk to your doctor.
They will be able to discuss the risks and benefits of all genetic testing with you and help you make the best decision for you and your family.
Remember that most children are born healthy, but it is important to understand your options and what genetic tests are available to you.
