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How do health care providers diagnose birth defects?

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Diagnosis of birth defects depends on the specific problem and parts of the body affected. For example, although their causes might not be easily detectable, structural birth defects such as clubfoot and cleft lip are visually noticeable at birth.

Other birth defects are not always detectable by looking at a newborn. Newborn screening, a process that tests infants’ blood for different health conditions, including many birth defects, provide one method of detecting problems before they have lifelong effects.

Infants who are at high risk for certain birth defects, for example, because of their family history, can undergo additional testing at birth to detect these conditions and treat them, if needed. This type of screening has been effective in detecting some cases of Menkes disease, allowing for treatment to begin before health problems occur.

Prenatal Screening

Health care providers recommend that certain pregnant women, including those who are older than 35 years of age and those with a family history of certain conditions, have their fetuses tested for birth defects prenatally, while still in the womb. There are two main types of prenatal tests for birth defects.


Amniocentesis (pronounced am-nee-oh-sen-TEE-sis) is a test that is usually performed to determine whether a fetus has a genetic disorder. In this test, a doctor takes a small amount of fluid from the womb using a long needle. The fluid, called amniotic (pronounced am-nee-OT-ik) fluid, contains cells that have genetic material that is the same as the fetus’s genetic material. A laboratory grows the cells and then examines their genetic material for any problems. Some birth defects that can be detected with amniocentesis are Down syndrome and certain types of muscular dystrophy.

Because amniocentesis can cause a miscarriage in about 1 out of 200 cases, it is usually only recommended for pregnancies in which the risk of genetic disorders or other problems is high.

Chorionic Villus Sampling (CVS)2,3

This test extracts cells from inside the womb to determine whether the fetus has a genetic disorder. Using a long needle, the doctor takes cells from the chorionic villi (pronounced KOHR-ee-on-ik VILL-i), which are tissues in the placenta, the organ in the womb that nourishes the fetus. The genetic material in the chorionic villus cells is identical to that of the fetal cells.

Like amniocentesis, CVS can be used to test for chromosomal disorders such as Down syndrome and other genetic problems. CVS can be done earlier in pregnancy than amniocentesis, but it is also associated with a higher risk of miscarriage—about 1 in 100 cases. Health care providers usually only recommend CVS in women who are at high risk.

Links to more information about prenatal testing are available in the Resources and Publications section of this topic.

  1. The Patient Education Institute. (2011, March 01). X-plain: Amniocentesis-reference summary. Retrieved on July 24, 2012, from (PDF - 259 KB) [top]
  2. Simpson, J. L., & Otano, L. (2007). Prenatal genetic diagnosis. In S. G. Gabbe, J. R. Niebyl, & J. L. Simpson (Eds.), Obstetrics: Normal and problem pregnancies (5th ed.). New York, NY: Churchill Livingstone. [top]
  3. American College of Obstetricians and Gynecologists. (2007). Invasive prenatal testing for aneuploidy. Washington, DC: Author. [top]

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