DOWN SYNDROME PREGNANCY AND DOWN SYNDROME SCREENING

Down Syndrome Screening – The Signs, Symptoms and Tests for a Down Syndrome Pregnancy

The section on Down Syndrome risk factors by mothers and fathers age has moved to here

QUICK OVERVIEW of the Down Syndrome Pregnancy Symptoms professionals look for.

DOWN SYNDROME PREGNANCY CONTENTS THIS PAGE:

• 1… You are not alone in your search for Down Syndrome pregnancy symptoms.

  2… Is there even one SYMPTOM of Down Syndrome Pregnancy that you can be sure of, one way or the other? 

  3… The soft, almost certain SIGN of Down Syndrome pregnancy – Down Syndrome Screening  tests   used for screening during the first trimester and second trimester of the pregnancy: 
  a.. Down Syndrome ULTRASOUND and nuchal translucency and missing nasal bone checks – the   stronger markers for Down Syndrome.
  b.. BLOOD TESTS for Downs Syndrome Screening.
  c.. The VERY SOFT ULTRASOUND SYMPTOMS of a Down Syndrome pregnancy – the very weak markers for Down Syndrome.

  4… The invasive, hard, set in concrete sign of Down Syndrome pregnancy – Down Syndrome Screening test of the baby’s placenta or umbilical blood or of the baby’s surrounding fluid:
  a.. AMNIOCENTESIS for Down Syndrome pregnancy.
  b.. CHORIONIC VILLUS sampling for Down Syndrome pregnancy.
  c.. PERCUTANEOUS UMBILICAL BLOOD SAMPLING (PUBS) for diagnosing a Down Syndrome pregnancy.

  5… Contact us if you need to.

2… Is there even one symptom of Down Syndrome Pregnancy that you can be sure of, one way or another?

As a mother, you wont be able to tell any difference.

Down Syndrome pregnancy symptoms will be like any other pregnancy symptoms.

We have five living kids and eight that died in utero. We can honestly say, there were no differences in the pregnancy symptoms of the one which had Down Syndrome.

What you have to do is rely on the medical experts to to pick up Down Syndrome pregnancy symptoms through their elaborate testing, which we explain next.

3… THE SOFT, ALMOST CERTAIN SIGN OF DOWN SYNDROME PREGNANCY – DOWN SYNDROME SCREENING TESTS : ULTRASOUND AND BLOOD TESTS.

What screening tests are used and when, is determined by a number of factors, the most pertinent one being age of fetus – the trimester periods of pregnancy:

a.. Down Syndrome SCREENING Tests in the First Trimester: The Markers for Down Syndrome the experts look for and when.

In the first trimester (trimester just means three months), you can expect to be sent for an ultrasound, as well as a blood test.

The ultrasound is to obtain nuchal translucency measurements – measurements of the skinfold of the neck of the baby – One of the Down Syndrome pregnancy symptoms is often a thickening of the skin fold in the neck of the baby.  The nuchal translucency is the most well known and used of the markers for Down Syndrome.

The blood test measures a set of biochemical markers for Down Syndrome that are often predictive of a Down syndrome pregnancy in first trimester.

By using these Down Syndrome screening tests, the otherwise undectable Down Syndrome pregnancy symptoms become detectable.

Error rates with Down Syndrome screening tests during pregnancy, first trimester:

Up to 90% of Down Syndrome pregnancies are detected using these Down Syndrome screening tests, the remaining 10% or so with a Down Syndrome pregnancy are not detected.

These Down Syndrome pregnancy symptoms do, however, give false detections as wells – around 5% of those detected as having a Down Syndrome pregnancy, in fact, do not have a baby with Down Syndrome.

Look for the nasal bone?

Although it is not well known about, there is another Down Syndrome ultrasound marker that may be worthwhile looking for.

According to a research report published in Lancet (2001;358:1665-67), 701 high risk fetuses at between 11 and 14 weeks gestation had ultrasounds. In 73% of Down Syndrome ultrasounds, the nasal bone was missing; the other 27% of Down Syndrome ultrasounds showed a nasal bone.

In terms of the normal fetus population, the nasal bone can be detected via ultrasound 99.5% of the time.

So if it is missing from the ultrasound, it is almost certain the baby has a chromosomal abnormality.

It was also reported that the nasal bone was missing in 11 out of the 20 babies with trisomy 18 ( also known as Edward’s syndrome ) and in 2 out of 8 fetuses with Turner’s syndrome.

In all cases of triple X syndrome, trisomy 13, Klinefelter’s syndrome or triploid, the nasal bone was not apparent either.

When these results have been confirmed, it is hoped that the false detection rate will be halved, with a slight improvement in genuine detection as well.

More about the first trimester Down Syndrome Pregnancy screening tests

For your information, Down Syndrome screening blood test alone has a 70.1% detection rate for a Down Syndrome pregnancy; the ultrasound alone has a 72.7% detection rate; using both gives a down syndrome pregnancy detection rate of 88.3% . Information from Cuckle and Van Lith (1999), Prenatal Diagnosis 19: 505-512

For DOWN SYNDROME BLOOD TEST ANALYSIS, 5-10 mL clotted blood sample taken from the mother, must be taken between 10 and 13 weeks gestation is required, but preferably no later than 12 weeks 0 days.
For DOWN SYNDROME ULTRASOUND TEST / SONAGRAM TEST, a Nuchal Translucency ultrasound scan must be conducted when the fetus is between 11 weeks 0 days and 13 weeks 6 days, but preferably no later than 12 weeks 0 days.

The following information on ultrasounds and blood test procedures for a Down Syndrome pregnancy may also be of some value:

Dr. MacRae, year 2000:
Ultrasound is to be seen as an additional tool in Down Syndrome pregnancy screening.

Ultrasound allows a greater detection rate earlier in the pregnancy of babies with Down Syndrome.

The new ultrasound technique is known as ” nuchal translucency “.

In Down Syndrome ultrasound, that is, prenatal, the babies with Down Syndrome have been found to have more soft tissue around the neck; the more soft tissue found throught the ultrasound, the greater the risk of Down Syndrome.

Things to note about the ultrasound measurement for Down Syndrome: The fetus must be in just the right position, between 11 and 14 weeks in the pregnancy, and the ultrasound machine able to measure in tenths of a millimeter. Also, the person using the ultrasound machine should be well experienced in the measurement of the soft tissue.

Assuming these ultrasound constraints are met, when the information is added to the blood test results, a more accurate risk of Down Syndrome can be obtained.

That is to detect around 90 percent of those babies with Down Syndrome, with only 1% to 2% of pregnant women needing to use the more invasive procedure of amniocentesis.

Dr. Kypros H. Nicolaides et al. 2005:
Essentially his findings concur with that of MacRae in relation to Down Syndrome pregnancy screening.

Ninety percent of babies with Down Syndrome can be detected within the first trimester of pregnancy using ultrasound and blood tests.

However, he also mentions that the screening has a false-positive rate of 5%. In other words, five out of every 100 babies that screen during the first trimester determines as having Down Syndrome, in fact do NOT have Down Syndrome.

b.. Down Syndrome Pregnancy Tests in the Second Trimester: What the experts look for and when.

Second trimester Down Syndrome screening of blood, blood sample must be taken between the 14 week 0 day to 20 week 6 days mark. Best time for blood sample is at the 16 week gestation age.

Often these blood tests for Down Syndrome are called the triple screen (also called the multiple marker test) and the alpha fetoprotein plus blood test, usually taken between 15 and 20 week mark of pregnancy.

These blood tests for Down Syndrome pregnancy ESTIMATE the risk of Down Syndrome based on biochemical markers in the mother’s blood and how these markers change during pregnancy as well as with the mother’s age.

c.. The VERY SOFT ULTRASOUND SYMPTOMS of a Down Syndrome pregnancy – the very weak markers for Down Syndrome throughout the pregnancy.

These ultrasound symptoms of a Down Syndrome pregnancy are so soft, that their value appears to be more in worrying the expectant mother:

1. Brain cysts
2. Shorter thigh
3. Shorter upper-arm bones
4. Reduced femus to humerus ratio (upper arm to thigh bone ratio)
5. Splayed toes – enlarged gap between big toe and next toe – may be seen on a Down Syndrome pregnancy ultrasound.
6. Bright spots on the bowel, or a bright bowel (echogenic bowel pattern), or anything that suggests a gastrointestinal defect, such as duodenal atresia (double bubble), in the ultrasound.
7. Bright spots on the heart, or any sign of a heart defect in the ultrasound
8. High fluid levels in the kidneys, as suggested by pyelectasis, a dilation – enlargement – of the kidneys

In fact, any health issue common in Down Syndrome, or any characteristic common to Down Syndrome, if picked up in the ultrasound, can be taken to be a soft sign of Down Syndrome! So the list of Down Syndrome pregnancy ultrasound symptoms can actually go on and on.

Certainly, one of these very soft markers for Down Syndrome on their own, are most likely meaningless for diagnosing a Down Syndrome pregnancy, but if several of these ultrasound markers should occur together, then the prognosis of Down Syndrome becomes much more real.

4… THE INVASIVE, HARD, SET IN CONCRETE SIGN OF DOWN SYNDROME PREGNANCY: AMNIOCENTESIS, PERCUTANEOUS UMBILICAL BLOOD SAMPLING (PUBS) AND CHORIONIC VILLUS SAMPLING.

a.. Chorionic villus sampling and determining a Down Syndrome pregnancy.

Chorionic villus sampling, also known as chorionic villus biopsy, is where a sample of tissue is taken at, ideally, the 11-12 week mark.

However, chorionic villus sampling can be performed from 9� weeks to 19 weeks gestation.

Chorionic villus sampling involves using ultrasound to guide the catheter – a thin tube, the worker inserts the catheter via the vagina and cervix to take a miniscule tissue sample from outside the developing sac (where the baby grows), that is, the sample is taken from the placenta.

Chorionic villus sampling carries a risk of causing miscarriage in 1 to 3% of pregnancies investigated and a minute risk of 1 per 3000 pregnancies investigated of causing birth defects: Primarily missing or shortened fingers or toes.

Chorionic villus sampling should not be used in pregnancies where spotting or bleeding has occured, or where Rh sensitization from a previous pregnancy has taken place.

The Chorionic villus sampling technique can accurately determine Down Syndrome, as well as many other genetic disorders.

Test results from chorionic villus sampling are normally back within 1 to 2 weeks.

There is a tiny risk that the tissue sample taken will be that of the mothers, in which case the Chorionic villus sampling test result is useless.

b.. Amniocentesis and determining a Down Syndrome pregnancy.

Amniocentesis is usually performed from 14 weeks on in the pregnancy.

An amniocentesis is where a small amount of fluid is taken from around the developing baby.

The procedure of amniocentesis involves using an ultrasound machine to assist the technician insert a needle through the mother’s abdomen, then the wall of the uterus (womb) and then into the fluid surrounding the baby, leaving the baby and placenta alone.

Amniocentesis requires about 15mls (3 teaspoons) of fluid to be extracted.

Amniocentesis results may take up to a month to come back, typically two weeks, but are also very accurate for diagnosing Down Syndrome.

The risk of miscarriage from the amniocentesis test is around 1 in 200 tests performed.

Please note that the normal rate of miscarriage for a 14 to 18 week old pregnancy is 2 to 3%. So, amniocentesis adds 1/2% to that figure for that gestation period.

For the 10 to 12 week mark, the normal miscarriage rate is around 2% and Chorionic villus sampling adds another 1 to 3% to that: 3 to 5% in total.

c.. Percutaneous umbilical blood sampling (PUBS) and determining a Down Syndrome pregnancy.

Percutaneous umbilical cord blood sampling is usually done when the fetus is 18 weeks or older.

Percutaneous umbilical blood sampling test uses a very thin needle, guided by ultrasound though the mother’s abdomen, to obtain a small amount of blood from the umbilical cord.

Risks of the percutaneous umbilical blood sampling technique are similiar to amniocentesis, with the risk of miscarriage from percutaneous umbilical blood sampling being about 1 to 2% in total.

The results of the percutaneous umbilical blood sampling are normally back within three days and are very accurate for diagnosing Down Syndrome, as percutaneous umbilical blood sampling uses the baby’s blood for testing.

5… Email us if you need to with any question about a Down Syndrome pregnancy.

I think I have covered everything on Down Syndrome pregnancy, but if you have any questions, please contact me.