Pregnancy Health and Safety (Prenatal Care)
Down Syndrome

How is Down syndrome diagnosed during a pregnancy?

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Answered 2008-05-07 01:56:53

A doctor will perform screening tests during the pregnancy in order to diagnose (and/or indicate a high risk of) Down syndrome of the fetus.

First trimester screening for Down syndome involves an ultrasound. In the ultrasound, they are looking for an increased space in the back of the fetal neck. An increased diameter is associated with chromosomal abnormalities. A blood test is performed to check for high levels of PAAP-A and hCG, two hormones that are produced by the fetus and passed into the mother's bloodstream. Women whose results are abnormal would be offered amniocentesis.

Also, researchers are now looking at whether the absence of a nasal bone in the fetus, shown by an ultrasound, may also indicate a higher risk of Down syndrome.

When Is It Done?

* Blood test between 9-11 weeks. * Ultrasound between 11-13 weeks. * Follow-up blood test and results reported between 16-18 weeks. Ultrasound and the blood test are simple (and the usual) procedures.

This involves a simple blood test (triple screen) which will measure three hormones produced by the fetus and is passed into the mother's bloodstream: alpha-fetoprotein (AFP), hCG, and estriol. Some doctors also measure the hormone inhibin-A (making it a quad screen). This blood test can also be used in conjunction with the first trimester screening, call "integrated screen", for the highest detection rate of chromosomal abnormalities but not all practitioners are equipped to test this way yet.

Abnormally low levels suggest an increased risk of Down syndrome, or other chromosomal defect. The triple screen cannot diagnose a birth defect; it can only indicate an increased risk. The false positive rate for the triple screen is extremely high. Any abnormal result means that further testing is required. This is done between the 15th and 18th weeks and results are available within one week.

Chorionic Villus Sampling (CVS) is performed in the first trimester. CVS is useful to detect disorders for which the technology exists such as Down syndrome. Occasionally both CVS and amniocentesis may be needed. It is performed between the 10th and 13th weeks of pregnancy. CVS is performed depending on the location of the placenta, the sample of cells is taken via the vagina and cervix or via a needle inserted in the abdominal wall. Test results are available in 3-5 days. Since the chorionic villi are of fetal origin, examining them can give a complete picture of the gentic makeup of the developing fetus.

Amniocentesis is more than 99 percent accurate in diagnosing, or ruling out which is much more likely, Down syndrome. It is recommended when:

* The mother is over 35 years old. * The couple has already had a child with a chromosomal abnormality. * The mother is a carrier of an X-linked genetic disorder. * Both parents are carriers of an autosomal recessive inherited disorder. * A parent is known to have a condition such as Huntington's chorea. * Fifth Desease or other fetal infection is suspected. * Results of a screen test turn out to be abnormal and evaluation of the amniotic fluid is necessary. * It is necessary to assess the maturity of the fetal lungs late in pregnancy. * The couple has another child or a close relative with a neural tube defect.

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Related Questions

How can down syndrome be diagnosed?

Amniocentesis, given during the second trimester of pregnancy, is used to detect/diagnose chromosomal disorders including Down's Syndrome.

Does alcohol have something to do with Down syndrome during a pregnancy?

No, but consuming alcohol during pregnancy can lead to impaired mental development in a condition called Fetal Alcohol Syndrome.

If a women with Down syndrome is pregnant what would be the negatives and the positives during the pregnancy?

A pregnancy with Down Syndrome would be the same as any other pregnancy. But, there's a chance that if the mother finds out that her child has Down Syndrome by having some testing done, she might become depressed.

How many people are diagnosed with down syndrome a year?

As of 2010, approximately 400,000 children in the US are diagnosed with Down syndrome each year.

Can medication for gallstones during pregnancy cause Down syndrome?

See the Related Link to a very good FAQ on the causes of Down syndrome.

Too much Y choromosome in urine during pregnancy?

Can cause down syndrome

What are the reasons for being checked during pregnancy to see if your fetus has Down syndrome?

It might be useful to know if your baby will have Down Syndrome. In that way, you can be prepared for it. Another option is so that you have the choice to terminate the pregnancy.

What is a risk factor for having a baby with Down syndrome?

risk of having a baby with Down syndrome increases with her increasing age. Two types of testing is available during a pregnancy to determine if the baby being carried has Down syndrome.

How do you get diagnosed with Down syndrome?

You are born with it, and it is a birth defect. Down Syndrome is caused by the addition of one chromosome, in the 21st chromosome.

Does duodenal atresia always mean Down syndrome?

No, there is a 30-40% chance of Down Syndrome when duodenal atresia is diagnosed.

What are some common causes of retardation?

There are many causes of retardation. These includes Down syndrome, velocariofacial syndrome, fetal alcohol syndrome, problems during pregnancy and other genetic disorders.

At what stage of a pregnancy does Down syndrome occur?

At conception.

If you are detected with Trisomy 21 during your pregnancy what should you do?

Raise the Down Syndrome child and love him or her. Love is the best medicne.

What is the diagnosis for Down syndrome?

It cannot be diagnosed, since it is in no way possible to contract.

What can be diagnosed by examining a karyotype of an individuals white blood cells?

Down Syndrome

If you are pregnant can taking drugs lead to having a baby with Down syndrome?

No, Down Syndrome is strictly a genetically inherited condition; though taking drugs during pregnancy can lead to other health problems for the baby.

What does high TSH level in pregnancy indicate?

that your baby has down syndrome

What age do the symptoms of down syndrome start appering?

Babies are born with Down Syndrome and it's highly unlikely that it would not be picked up at birth. It is often diagnosed in utero

How many people have down syndrome in Mexico?

2009 statistics show over 131,199 people in Mexico were diagnosed with down syndrome, or 3.73 cases per 10,000 births.

How many people are diagnosed with Down syndrome per year?

1 in 800 births in the US

How is Down syndrome diagnosed?

Down syndrome is most commonly diagnosed by a geneticist. They will take a sample of DNA and view it on a micro-array or other similar methods. Ultimately they look for a third copy of chromosome 21. Every human has 2 copies of all (non sex) chromosomes and having a third or trisomy of chromosome 21 is confirmation of Down syndrome.

How can you prevent giving birth to a child with Down syndrome?

It is not possible to avoid having a pregnancy that carries a baby with Down syndrome. It is only during pregnancy that some tests can be done -- like triple (blood) test; amniocentesis (Fisher test) -- (after 12 weeks, 16-18 weeks of pregnancy), to know if the baby has Downs or not. Depending on the test results, one can decide to abort if it happens to be Down baby.

How early can Down syndrome be detected?

A new test has been developed, called FASTER (First and Second Trimester Evaluation Risk), with which Down syndrome will be able to be detected during the first trimester of the pregnancy - about 11 weeks after conception - with 87% accuracy.

What is he best way to test before pregnancy if the child will have Down syndrome?


What does it mean when the human ears are below the average parallel level with the eyes?

Mother drinking and drugging during pregnancy. Is what it is.

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