What is Genetic Carrier Screening Test and How is it Done?

The outcome of a pregnancy has a significant impact in your upcoming life. So most parents are open minded to anything and everything they can to to ensure a healthy baby. Now a days, most of the parents are aware of the screening tests conducted in the course of pregnancy, some of which are routine and some are exceptional, to avoid many dangerous outcomes of the pregnancy.

Much the same as physiological, many times, the baby is inclined to experience certain genetic disorders. Even though most of these disorders are rare in the general population, they are more common in certain nationalities and races. Genetic disorders have no cure, but they can be prevented. On account of advances in hereditary research, numerous recessive genetic disorders can be recognized through a specialized screening – carrier screening.

In This Article

• What is Genetic Carrier Screening Test?
• When Should You Get the Genetic Carrier Screening Test Done?
• List of Diseases That Parents Are Screened For
• What do the Carrier Screening Tests Results Convey?
• What if Both Parents Are Carriers?
• Prenatal Diagnostic Tests
• What if the Fetus Tests Positive For the Disease?

What is Genetic Carrier Screening Test?

Carrier screening is a screen test conducted to evaluate the chances of your baby inheriting serious genetic disorders of which either one or both parents are the carriers. Here is the basic concept of this screening test:

A ‘carrier’ is referred to as a person whose one gene of the pair of the chromosome has an inherited disorder, while the other one remains normal. As a result, the person, though, has disease trait, possesses no physical symptom of the disease. However, if a person who is a carrier of a serious hereditary issue has a baby with another person who is also a carrier of the same hereditary issue , their baby has increased chances of inheriting a defective gene from each parent to have the disease.

When Should You Get the Genetic Carrier Screening Test Done?

Ideally, you should be offered the test before, that is, during your first preconception appointment. If you carry a risk of being a carrier of genetic disorders, and so does your partner, your baby will have a 1 in 4 chance of getting the defective gene and being born with the disorder. Talking to a genetic counselor to figure out your whether you should reproduce or adopt can help too.

List of Diseases That Parents Are Screened For

Some of the more common hereditary conditions that carrier screening tests for are:

1. Fragile X Syndrome

Fragile X syndrome is a genetic disease that causes intellectual disabilities. It is brought about by a defect in the gene located on the X-chromosome.

2. Sickle Cell Disease

Our body needs enough red blood cells to carry oxygen throughout our whole body. But sickle cell anemia prevents the same. Being an inherited form of red blood cell disorder people with the disease do not have enough healthy red blood cells to carry oxygen. If the mother is a carrier, the father will be screen tested as well. If both mother and father have the problematic gene, then the chances of the baby to experience sickle cell disease is 25%.

3. Tay- Sachs

Tay-Sachs is a rare genetic disorder that eventually destroys neurons (nerve cells) in the brain and spinal cord.

4. Spinal Muscular Atrophy

Spinal muscular atrophy (SMA) is a genetic disease. This disorder has an impact on the area of the nervous system that controls voluntary muscle movement. Decaying of motor neurons, the nerve cell found in the spinal cord is the cause of this condition.

5. Cystic Fibrosis

Cystic fibrosis is a potentially fatal genetic disorder and one of the most commonly found genetic disorder. In this condition, the lungs can be severely damaged. Digestive issues and other complications are also associated with cystic fibrosis.

6. Familial Dysautonomia

Familial dysautonomia is a genetic disorder. It affects cells in the autonomic nervous system that controls involuntary actions like digestion, regulating body temperature, breathing, production of tears, and also regulating the blood pressure.

7. Thalassemia

Thalassemia is a collective name for inherited blood disorders, some of which cause relatively mild and others that may bring about severe anemia and other significant issues.

8. Canavan Disease

Canavan disease is a rare inherited disorder. It destroys the capacity of nerve cells (neurons) in the brain to send and receive messages.

[Read : Premenstrual Dysphoric Disorder Treatment]

What do the Carrier Screening Tests Results Convey?

Mostly, both parents are screened at the same time or each one in turn. Your blood sample will taken and sent to a lab where it is examined for the proof of hereditary anomalies. Results take around a couple of weeks.

1. When one of the parents’ tests positive for an autosomal recessive disorder, but the other one tests negative, the baby will not be conceived with the disorder. However, the baby possesses a 50% chance of being a carrier.
2. In the event that you and your partner are both carriers of a similar recessive disorder, there is a 25% chance that your baby will be conceived with that disorder. There is a half shot that your baby will be a carrier showing no specific indication of the disorder, and a 25% possibility that your baby will not acquire the disorder from either parent.

What if Both Parents Are Carriers?

When both the parents are carriers of the same recessive disease, your baby has a 25% chance to conceive with that issue. Likewise, there is a 50% possibility that your child will be a carrier, showing no symptoms of the disease and another 25% chance not to inherit the problematic gene from either parent.

Technology in the reproductive field is highly developed. Preimplantation Genetic Diagnosis (PGD), which is a procedure used before the implantation of the embryo to recognize hereditary imperfections inside the embryo, is created through in vitro fertilization (IVF), to prevent a certain genetic disorder from passing on to the baby. Artificial insemination happens when the sperm is received from a donor without the problematic gene. Adoption is another option. Getting pregnant and undergoing prenatal diagnostic testing can also be done.

[Read : Getting PGS And PGD Before IVF Treatment]

Prenatal Diagnostic Tests

The prenatal diagnostic test is a screening test conducted to find out if the fetus is affected by the hereditary disease of which the parents are the carrier(s). High degree of accuracy of diagnosis is guaranteed in chronic villus sampling, which is done between the 10th to 12th week of gestation or amniocentesis after the 15th week of gestation. Deciding the apt test belongs to your doctor.

What if the Fetus Tests Positive For the Disease?

Though a high degree of accuracy is guaranteed, the prenatal test has its own limitation. These tests are not able to determine the range of severity of the condition, which is important to take an appropriate decision regarding the pregnancy.

Read Also: Your Comprehensive Guide To An IVF Treatment