Genetic testing during pregnancy can be a lot helpful in determining the health of your baby. While some of the genetic tests are specifically meant to check for certain medical conditions, others can help to diagnose any genetic disease while the baby is still in the womb. Note that most of the genetic tests are optional to the mothers, but experts at community healthcare centers always recommend these to make the right health decisions as required after childbirth.

Genetic Carrier Screening Tests

These tests are done before pregnancy to figure out if you or your partner has a defective gene that you could pass on to your child. It is not necessary to show the symptoms of any disorder if you have only one defective gene, but that makes you a potential carrier. For a genetic carrier screening, the doctor would take a sample of your saliva or blood and send it to a specialized laboratory for analysis.

The common types of disorders doctors look for here are Fragile X syndrome, Cystic Fibrosis, Tay-Sachs disease, Spinal Muscular Atrophy, and sickle cell disease. The screening test can also be done during the first few weeks of pregnancy, but it is usually recommended before conceiving.

First Trimester Screening Tests

The doctor might recommend a few tests in the first trimester to check the baby’s genes and see if there is any risk of a medical condition. Some of the common genetic tests recommended during the first three months of pregnancy are:

  • Sequential screening – This test is done to check the risk of trisomy 18, Down syndrome, as well as any other spine and brain conditions. The test uses a combination of blood tests and ultrasound scanning, and it is suggested between 10 and 13 weeks. Sometimes, the doctor might ask for a follow-up test in the second trimester as well.
  • Integrated screening – This test also uses a combination of blood tests and ultrasound scanning and is done around 12 weeks of pregnancy to check for the same health problems as stated above. It is more precise than sequential screening though, yet it still requires a follow-up test in the second trimester to confirm the results.
  • Cell-free fetal DNA testing – This test is done to check for trisomy 13, trisomy 18, problems related to sex chromosomes, and Down syndrome. This is done using a blood test, and if any risk of a birth defect were found, the doctor would recommend a diagnostic test to determine the course of action.

Second Trimester Screening Tests

During the 13 to 28 weeks of pregnancy, the doctor would recommend a few typical tests to check the growth and health of the baby as well as to find out any risks of genetic disorders. Some of the common tests recommended during the second trimester are:

  • Maternal serum quad screening – This test is done to check the protein levels in your blood and assess the risk of trisomy 18, Down syndrome, as well as other brain or spine problems. The blood test is recommended between 15 and 21 weeks of pregnancy.
  • Ultrasound scan – This is done around 20 weeks of pregnancy to get images of the baby. The doctor would use the picture to check for birth defects such as cleft palate and heart or kidney problems.
  • Diagnostic tests – Doctors recommend amniocentesis and CVS (Chorionic Villus Sampling) to mothers in their second trimester. These diagnostic tests are done to check for trisomy 13, trisomy 18, problems related to brain or spine growth such as spina bifida, and Down syndrome. Both the tests are very reliable and accurate.

Note that diagnostic tests like CVS and amniocentesis carry a minor risk of causing a miscarriage, which is why most women do not prefer these to be done. Besides, they also feel more comfortable with the screening tests, and are satisfied with the results they provide. Yet again, no screening test can be as accurate as a diagnostic test. Therefore, it is better to consult with the expert at the community healthcare solution and weigh all your options before making a decision.

  • CVS involves testing a small sample of the placenta, which the doctor takes either through the stomach using a needle or through a thin tube inserted into the cervix. The diagnostic test can be done in the early stages of pregnancy as well to minimize the issues like cramps or bleeding.
  • Amniocentesis involves testing a sample of the amniotic sac fluid. The doctor inserts a thin needle through the belly to take the sample and then sends it to a specialized laboratory to analyze the protein content in the fluid. The diagnostic test is done between 15 and 20 weeks of pregnancy.

If your doctor suggests CVS or amniocentesis, it is not necessary that your baby is at risk of a genetic disorder. Usually, doctors recommend these diagnostic tests to confirm the findings of a screening test and ensure that everything is fine.

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    About the Author

    Dr. Ghassan M. Al-Jazayrly, MD

    A graduate of University of Aleppo Faculty of Medicine, Dr. Al-Jazayrly or, as he is colloquially known: Dr. AJ, is an oncologist and hematologist of a Complete Care Community Health Center (CCCHC) with more than 36 years of experience. In recent years, he’s been involved with a non profit organization known as Every Woman Counts (EWC) which provides free breast and cervical cancer screening and diagnostic services to California’s underserved populations in order to eliminate health disparities for low-income individuals.

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