Health care providers can bank check for Down's syndrome during pregnancy or later a child is built-in. There are two types of tests for Down syndrome during pregnancy:

  • A prenatal screening exam. This test tin can evidence an increased likelihood that a fetus has Down syndrome, only it cannot determine Downward syndrome is definitely present. If a screening test shows an increased likelihood, a diagnostic test tin be ordered.
  • A prenatal diagnostic exam. This test tin can determine with certainty that Down syndrome is nowadays. Diagnostic tests bear a slightly greater chance to the fetus than practise screening tests.

The American Congress of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women exist offered a Down's syndrome screening examination.ane

Prenatal Screening for Down syndrome

At that place are several options for Down syndrome prenatal screening. These include:

  • A blood test and an ultrasound test during the beginning trimester of pregnancy. This is the most accustomed approach for screening during the first trimester. A claret test enables a health care provider to bank check for "markers," such equally certain proteins, in the mother's blood that propose an increased likelihood of Down syndrome.2 And then the health care provider does an ultrasound test, which uses high-frequency sound waves to create images. An ultrasound can notice fluid at the back of a fetus's cervix, which sometimes indicates Down syndrome. The ultrasound test is called measurement of nuchal translucency. During the kickoff trimester, this combined method results in more than effective or comparable detection rates than methods used during the 2nd trimester.3
  • A blood test during the second trimester of pregnancy. Equally in the first trimester, a blood test enables a health care provider to bank check for markers in the female parent's claret. A triple screen looks for levels of 3 different markers; a quadruple screen looks for levels of four different markers.3,4
  • A combined examination (sometimes called an integrated test). This approach uses both a blood test and an ultrasound during the first trimester also as a second-trimester blood examination. Health intendance providers then combine all these results to produce one Down syndrome risk rating.2

If a woman is pregnant with twins or triplets, a blood test will not exist every bit reliable because the substances from a Down's syndrome fetus may be harder to detect.2,3

Prenatal Diagnostic Testing for Down Syndrome

If a screening test suggests the likelihood of Down's syndrome, a diagnostic test can be performed. ACOG recommends that pregnant women of all ages be given the option of skipping the screening examination and getting a diagnostic test first. Until recently, only women over age 35 and other at-risk women were offered this option because diagnostic tests carry a slight risk of miscarriage.1 Earlier having diagnostic testing, a significant woman and her family may want to meet with a genetic counselor to discuss their family history and the risks and benefits of testing in their specific situation.

Diagnostic testing for Down syndrome involves removing a sample of genetic cloth. Later on it is removed, the sample is checked for extra material from chromosome 21, which may indicate that a fetus has Down's syndrome. Parents usually get the results of the test a week or ii later. The following procedures are used to extract samples.

  • Amniocentesis (pronounced am-nee-oh-sen-TEE-sister). A health care provider takes a sample of amniotic (pronounced am-nee-OT-ik) fluid, which is then tested for the extra chromosome. This test cannot be done until week 14 to 18 of the pregnancy.
  • Chorionic villus (pronounced KOHR-ee-on-ik VIL-uhs) sampling (CVS). A health care provider takes a sample of cells from a function of the placenta (pronounced pluh-SEN-tuh), which is the organ that connects a woman and her fetus, and then tests the sample for the actress chromosome. This test is done between weeks 9 and xi of pregnancy.
  • Percutaneous (pronounced pur-kyoo-TEY-nee-uhs) umbilical blood sampling (PUBS). A health care provider takes a sample of fetal blood in the umbilical cord through the uterus. The blood is then tested for the extra chromosome. PUBS is the most accurate diagnostic method and tin confirm the results of CVS or amniocentesis. However, PUBS cannot be performed until later in the pregnancy, during the 18th to 22nd week.5

Prenatal diagnostic testing does involve some risk to the female parent and fetus, including a slight take a chance of miscarriage.half dozen,7,8,nine If you and your family are considering prenatal diagnostic testing for Down syndrome, discuss all the risks and benefits with your health intendance provider.

Chromosomal Testing of Maternal Claret

A significant woman who is at risk for having an infant with Down's syndrome besides can have a chromosomal test using her blood. A mother's claret carries DNA from the fetus, which may show extra chromosome 21 material.3 A more invasive exam then would usually confirm the blood examination.

Testing and In Vitro Fertilization

Another approach to diagnosis is used in conjunction with in vitro fertilization. Preimplantation genetic diagnosis (PGD) allows clinicians to detect chromosome imbalances or other genetic atmospheric condition in a fertilized egg before information technology is implanted into the uterus.

This technique is useful mostly for couples who are at gamble of passing on a diverseness of genetic conditions, including X-linked disorders, too as couples who accept suffered repeated spontaneous pregnancy losses, sub-fertile couples, or those at risk for single-gene disorders.

Those interested in PGD should have genetic counseling and should consider close monitoring and additional testing during their pregnancies, given some increased adventure of chromosomal abnormalities arising secondary to the in vitro fertilization procedure.10

Diagnosis of Down Syndrome After Nascency

A diagnosis of Down's syndrome after nascence is often based initially on physical signs of the syndrome.

But considering individuals with Down syndrome may not have these symptoms, and because many of these symptoms are common in the general population, the health care provider volition accept a sample of the baby'southward blood to confirm the diagnosis. The claret sample is analyzed to determine the number of the babe's chromosomes.11

Citations

Shut Citations

  1. American Congress of Obstetricians and Gynecologists (ACOG). (2007, May 7). ACOG'south screening guidelines on chromosomal abnormalities [News release]. Retrieved June 11, 2012.
  2. Driscoll, D. A., & Gross, Southward. (2009). Prenatal screening for aneuploidy. New England Journal of Medicine, 360, 2556–2562.
  3. Ehrich, 1000., Deciu, C., Zwiefelhofer, C., Tynan, J. A., Cagasan, L., Tim, R., Lu, V., et al. (2011). Noninvasive detection of fetal trisomy 21 by sequencing of DNA in maternal blood: A study in a clinical setting. American Periodical of Obstetrics & Gynecology, 204, 201–211.
  4. ACOG. (2011). Routine tests in pregnancy. Retrieved June 11, 2012, from http://www.acog.org/~/media/For%20Patients/faq133.pdf?dmc=i&ts=20120611T1510306056 External Web Site Policy (PDF - 218.20 KB)
  5. American Association for Clinical Chemistry. (2012). Second trimester: Cordocentesis (percutaneous umbilical claret cord sampling, PUBS). Retrieved June xi, 2012, from https://labtestsonline.org/conditions/pregnancy-2d-trimester-13-27-weeks External Web Site Policy
  6. Caughey, A. B., Hopkins, L. M., & Norton, M. E. (2006). Chorionic villus sampling compared with amniocentesis and the difference in the rate of pregnancy loss. Obstetrics and Gynecology, 108, 612–616.
  7. Evans, M. I., & Wapner, R. J. (2005). Invasive prenatal diagnostic procedures 2005. Seminars in Perinatology, 29, 215–218.
  8. Daniilidis, A., Karydas, H., Zournatzi, V., Tantanasis, T., Giannoulis, C., & Tzafettas, J. (2008). A four-year retrospective study of amniocentesis: 1 centre experience. Hippokratia, 12, 113–115.
  9. ACOG. (2007). ACOG Practise bulletin: Invasive prenatal testing for aneuploidy. Retrieved June xi, 2012, from https://www.ncbi.nlm.nih.gov/pubmed/18055749 (PDF - 160 KB)
  10. Hanna, K. E. (2006). Reproductive genetic testing. Retrieved June 11, 2012, from the National Human Genome Research Institute website: http://www.genome.gov/10004766
  11. National Human Genome Inquiry Institute. (2010). Learning about Down's syndrome . Retrieved June eleven, 2012, from http://world wide web.genome.gov/19517824#3

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