Pregnancy testing for birth defects

Pregnancy tests such as nuchal translucensy screening can help detect birth defects.

Contents 1 Types of pregnancy tests 2 Pregnancy tests in the first trimester 3 Pregnancy tests in the second trimester 4 Pregnancy tests in the third trimester 5 References

[edit] Types of pregnancy tests

Birth defects occur in the fetus usually due to congenital disorders or improper formation of organs and limbs. Birth defects detected by pregnancy testing may be anywhere between non-critical and crippling. Some of these may be treatable, some not. You need to make the right choices as these will impact the life of your to-be-born child. There are two types of pregnancy testing: screening tests – to determine the chances of certain birth defects – and diagnostic tests – to reveal more about any specific birth defects.

[edit] Pregnancy tests in the first trimester

According to a paper published by The American Congress of Obstetricians and Gynecologists, most birth defects occur in first three months of pregnancy. Your doctor may recommend some of these, only if required. The most common screening tests done during this period are:

• Nuchal translucency screening: This is an ultrasound test to determine the thickness of the back of the fetus’ neck.
• Blood tests: Blood tests for pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG) are usually done along with the above screening.

Any anomaly in the result of the above two sets of tests in combination may provide indications of Down’s Syndrome, trisomy 18, trisomy 13, and any such chromosome-related birth defects. If there is an indication of any chromosome-related birth defects, chorionic villus sampling (CVS), a diagnostic pregnancy test for birth defects, may be recommended.

Pregnancy testing in the first trimester is usually done between weeks 10 and 13.

[edit] Pregnancy tests in the second trimester

There is a quad screening test for maternal blood which checks four substances: alpha-fetoprotein (AFP), beta-hCG, a type of estrogen, and inhibin A. The results of these tests help predicting the likelihood of chromosome-related disorders in the fetus.

An ultrasound test is usually recommended to investigate further into any chromosomal birth defects or any other structural birth defects in the fetus.

In the second trimester of pregnancy a diagnostic test, aminocentesis, may be recommended if there is a high chance of the fetus having birth defects like Down Syndrome, Tay-Sachs and similar disorders. Aminocentesis is a test for chromosome-related disorders as well as open neural tube defects. It is done by testing the cells shed by the fetus into the amniotic fluid.

Pregnancy testing in the second trimester is usually done between weeks 15 and 20.

[edit] Pregnancy tests in the third trimester

In the third trimester, between weeks 24 and 28 expectant women are recommended to undergo glucose tolerance test to test the levels of sugar or glucose in the blood stream. An abnormally high level of sugar indicates gestational diabetes. In the late weeks of pregnancy and during labor, fetal heart beat rate is checked and monitored to determine if the condition of the fetus is stable or needs any emergency intervention.

Remember, most mothers-to-be usually need to undergo only routine tests. Complex pregnancy testing for birth defects would be recommended by doctors only if they sense any abnormality, not otherwise. You may be recommended to undergo many of these pregnancy tests so that you can make an informed decision and have a choice in the birth of your child in case of critical birth defects.

[edit] References

• http://www.medicinenet.com/down_syndrome/article.htm#what
• http://www.medicinenet.com/script/main/art.asp?articlekey=10106
• http://www.lpch.org/DiseaseHealthInfo/HealthLibrary/pregnant/tests.html
• http://www.webmd.com/baby/tc/birth-defects-testing-what-are-the-tests
• http://www.acog.org/publications/patient_education/bp165.cfm
• http://kidshealth.org/parent/system/medical/prenatal_tests.html#

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