Screening & Testing

Neural tube defects screening tests are designed to help identify the risk of birth defects in the mother before the fetus has developed too far. While most screening tests cannot actually diagnose a real defect, they can test blood levels to determine the likelihood that a neural defect has occurred. There are many tests that can be done, including the maternal blood test, the AFP, the triple screen or quad screen, and visual testing through x-ray and MRI scans.

Maternal Blood Test Screening

During this test, a blood sample is taken from the arm of the pregnant woman. The blood can then be tested for certain levels of alphfetoprotein to determine if a baby will have a higher risk of neural tube defects as well as chromosomal health risks like Down’s Syndrome. The test is usually performed in the first or second trimester, and has been known to cause many ‘false positives’. These tests are not conclusive and should only be used to determine risk. Once that is established, other testing needs to be done to visually diagnose an NTD.

Acetylcholinesterase

Another level that is checked is the acetylcholinesterase, which can be tested through the amniotic fluid. Once again, the levels will be checked to rule out different chromosomal issues and neural tube defects. Again, this screening is strictly risk-based and not a definitive measure for diagnosis.

Triple/Quad Screen

This test is generally ordered during the second trimester of pregnancy, and is used to help determine the level of risk that a fetus faces for different abnormalities. It combines three or four substance levels in the test to determine a risk level through mathematical formulas. The substances tested include AFP, hCG, unconjugated estriol, and often inhibin A. When the levels are calculated they can give a very distinct result of the risk that is held by the fetus for developing abnormalities and defects like neural tube defects. Test results should always be provided by a clinician or genetic specialist who understands the test and can help recommend follow-up options. This is yet another test to determine risk, not diagnose.

Ultrasound

As with any health issue related to baby, ultrasounds are always an effective testing tool. These scans give a visual image of the fetus in development that allows the doctor to see defects and deformities as they are occurring or shortly after they are created. This helps to diagnose neural tube defects quicker and determine the next right course of action.

X-Ray, MRI and CT Scans

Other imaging tests are often ordered after birth or even during pregnancy to ensure that the baby is not under more severe risk than originally presumed. X-rays, CT scans and MRIs can all help clarify the deformity seen on the ultrasound or provide testing options for babies who are born and believed to have some type of deformity or birth defect. These tests are conclusive in diagnosis and can be ordered for a variety of different reasons.

Conclusion

Once testing has been completed, the doctor will then help the mother determine the next course of action. If no defects are found, nothing needs to happen and things can carry on. However, if the screening tests indicate that risk levels are high, doctors might order more testing. If visual imaging tests diagnose a neural tube defect, the doctor may advise on different options that the mother has for her pregnancy, including termination in the most severe cases where the fetus will die, be stillborn, or the mother’s life will be put in jeopardy. Therefore, getting the most accurate test results is critical before making a decision about how to proceed with neural tube defects.

References:

http://www.marchofdimes.com/Pregnancy/prenatalcare_blood.html

http://www.labtestsonline.org/understanding/analytes/triple_screen/test.html

http://www.labtestsonline.org/understanding/conditions/neural_tube-3.html

This entry was posted in Neural Tube Defect FYI. Bookmark the permalink.

Comments are closed.