Testing for down syndrome

My wife is pregnant 3 months. I will have a DRAGON BABY. Yesterday doctor suggest to do blood test to test for down syndrome. Why? because my wife above 35 years old. RM 380 walau wei sipeh expensive.

I think this is the test:

FTS is a non-invasive screening test carried out on maternal serum obtained in first trimester pregnancy (between  11w0d and 13w6d gestation), to provide a service involves a risk calculation derived from combination of two biochemical placental markers; free Beta  hCG and PAPP-A combined with the ultrasound marker Nuchal  Translucency (11w0d-13w6d gestation) for the  screening of the three most common fetal chromosomal abnormalities, namely,  Trisomy 21(Down’s Syndrome), Trisomy 18 (Edwards’ Syndrome),  and Trisomy 13 (Patau’s Syndrome).  Detection rate >90%1

 What is the test for????

Why test for Down's syndrome? Down's syndrome is the most common chromosomal abnormality and can have a major impact on a family, so testing for it in pregnancy have been available for some time. Tests are especially offered to pregnant women over the age of 35. Older women are more likely than younger ones to have a baby with Down's syndrome. There are two types of test available. A screening test estimates the risk of your baby having Down's. A diagnostic test, such as CVS or amniocentesis, can give you a definite diagnosis, but also carries a small risk of miscarriage. What screening tests are available? There are many different screening tests available in the private sector (but not in government hospitals or clinics). You will have to pay for them. There are ultrasound tests, blood tests and a combination of the two. Remember that these are screening tests. They can't tell you for certain that your baby has or has not got Down's syndrome. A screening test can help you decide whether or not to have a diagnostic test. A cut-off point of 1 in 250 is usually used. If your risk is less than that, you will be described as "screen negative" which means that you are unlikely to be carrying a baby with Down's (but it's not impossible). The tests will detect many pregnancies affected by Down's syndrome, but they will also identify some pregnancies as being at risk of Down's syndrome when, in fact, they are not; these are known as "false-positives". First trimester screening From 11 to 14 weeks of pregnancy, an ultrasound scan called a nuchal translucency (NT) scan can be performed. During an NT scan, the doctor measures the fluid under the skin at the back of your baby's neck. This can be used to determine your risk of having a baby with Down's syndrome. There is also a blood test which you can have either in combination with the NT scan (the combined test) or on its own. The blood test measures: hCG (human chorionic gonadotrophin); PAPP-A (pregnancy associated plasma protein). A woman who is carrying a baby with Down's syndrome will have abnormal levels of these two substances in her blood. These tests are pretty accurate on their own but become even more accurate if combined. The NT scan alone probably picks up about 75 to 82 per cent of babies with Down's syndrome, and the blood test alone, about 60 to 70 per cent. If you put the two tests together, the detection rate is usually in the range of 90 to 93 per cent with about a 3 to 5 per cent false positive rate. However, the accuracy of the combined test depends on many factors, such as the training of the person performing the scan and how good the scanner is that she's using. Plus the timings of the blood tests and the NT scan can also make a difference to detection rates. Advantages of first trimester screening Good detection rates. You have time to think about what you want to do next if you are found to be at high risk for Down's. Your options include doing nothing or having a diagnostic test, such as CVS or amniocentesis, to tell you for certain if your baby has Down's. You, your husband and doctor can then discuss the next course of action. Disadvantages of first trimester screening NT scans are not available everywhere, and many doctors are not accredited or suitably trained to perform them. The combined NT and blood test is only available in the private sector and is expensive.

The risk of Down syndrome is increased with increasing age. For example, the risk of having a baby with Down syndrome is one in a thousand for a 30 year old compared with one in a hundred in a 40 year old (see table below). The risk is also increased if there is a history of Down syndrome in the family.
Age Mother (years)Risk of Trisomy 21Risk of all chromosomal Abnormality
201 in 16671 in 526
221 in 14291 in 500
241 in 12501 in 476
261 in 11761 in 476
281 in 10531 in 435
301 in 9521 in 384
321 in 7691 in 323
341 in 5001 in 238
351 in 3851 in 192
361 in 2941 in 156
371 in 2271 in 127
381 in 1751 in 102
401 in 1061 in 66
411 in 811 in 53
421 in 641 in 42
431 in 501 in 33
451 in 301 in 21
461 in 231 in 16
471 in 181 in 13
481 in 141 in 10
491 in 111 in 8
Reference: Hook EB. Rates of chromosomal abnormalities at different maternal ages. Obstetrics and Gynecology, 1981;58:282-285 and Hook EB, Cross PK and Schreinemachers DM. Chromosome abnormality rates at amniocentesis and in liveborn infants. Journal of the American Medical Association, 1983;249:2034-2038.
What tests are currently available for Down syndrome?
Two types of tests are available; screening tests and diagnostic tests. Screening tests for Down syndrome include the biochemical tests (e.g. double, triple or quadruple tests) and ultrasound scan (11-13+6 weeks nuchal scan).

Diagnostic tests include amniocentesis and chorionic villous sampling. Since diagnostic tests are "invasive" (involves sampling with a needle or small cannula / tubing) there is a procedure-related risk of miscarriage between 0.5 to 1%. However, screening tests do not jeopardize the pregnancy as they are "non-invasive".

More about Nasal Bone and Nuchal Translucency:

What is crown to rump length (CRL)?

The crown rump length is a universally recognized term, very useful for measuring early pregnancies. The CRL (see image above between the two white + marked 1) is highly reproducible and is the single most accurate measure of gestational age. Charts have been developed for this purpose, but some simple rules of thumb can also be effectively used. From 6 to 11 weeks gestational age, the fetal CRL grows at a rate of about 1 mm per day.

Crown Rump Length:
Gestational age = 6 weeks plus (CRL x days). For example, a CRL of 23 mm would correspond to a gestational age of 9 weeks and two days (6 weeks plus 23 days = 9 weeks and 2 days). Accuracy of CRL after 12 weeks in predicting gestational age diminishes and is replaced by measurement of the width of the fetal head (biparietal diameter or BPD).

NT Scan

What is the Nuchal Translucency?

The nuchal translucency (also spelled nucal translucency) is a collection of fluid beneath the fetal skin in the region of the fetal neck and this is present and seen in all fetuses in early pregnancy. The fluid collection is however increased in many fetuses with Down's syndrome and many other chromosomal abnormalities. It is called a 'translucency' because on ultrasound this appears as a black space beneath the fetal skin. It is this black space that you will see measured during the ultrasound scan.

Currently the most accurate non invasive test for detecting Down syndrome during pregnancy is the measurement of the nuchal translucency with an ultrasound between 11 to 14 weeks of pregnancy. This is normally less than 2.5mm and when seen increased (greater than 2.5mm, see image on the right) may indicate the baby has Down syndrome or may indicate another chromosomal abnormality. 95% of measurements will indicate a reduced risk.

MY BABY is 1.4 mm.


Fetal Nasal Bone

Nasal BoneThe nuchal translucency test will also check whether your baby has a visible nasal bone. In the past few years it has been seen that approximately 3 in 4 babies with Down's syndrome do not have a visible nasal bone at the time of the first trimester screening test. If the nasal bone is visible at the scan then this will reduce the chance of your baby having Down's syndrome.

The view of the nasal bone should show three distinct lines:
• The first two lines, are horizontal and parallel to each other, resembling an 'equal sign'. The top line represents the skin and bottom one, represents the nasal bone.
• A third line, almost in continuity with the skin, but at a higher level, represents the tip of the nose.

Occasionally the nasal bone cannot be seen at 11 weeks as it is too early in the pregnancy.
If this is the case and this creates some concern then the scan can be repeated a week later.

Aiya, I think doctor didn't check for this one.

Next time must ask.