What is Ultrasound?
Ultrasound technology allows medical professionals to look inside a patient without resorting to surgery. A transmitter is used to send high frequency sound waves in the body; the waves bounce off the different tissues and organs and hence produce a unique pattern of echoes. A receiver attached, hears the returning echo pattern and it sends it to a computer translating the data into an image on a television screen. Ultrasound can differentiate subtle variations between soft and fluid-filled tissues and is very useful in providing diagnostic images of the abdomen.
Ultrazvuk abdomena is non-ionizing radiation hence it has no known negative effects. It is often used in conjunction with other imaging techniques. Ultrasound, x-ray, and magnetic resonance imaging (MRI) takes body images using diverse technologies and every technique is quite helpful in determining mass properties resulting in more complete diagnosis.
Ultrasounds and detecting Down Syndrome
Ultrasound tests can be done in the first trimester to check for early signs of Down's Syndrome, such as thicker than normal neck skin. You have an ultrasound scan and the radiographer or doctor measures the amount of fluid beneath the skin behind the baby's neck. This measurement can indicate the possibility of the baby having Down's syndrome.
In the early second trimester, an ultrasound test may be able to show another potentially problematic sign, the lack of a normal nasal bone.
Ultrasound is not a definitive test for a number of reasons. The mother will be moving slightly during the test, no matter how hard she tries to be still. Her breathing moves her uterus, if nothing else. In addition, of course, babies move around like mad as any pregnant lady who's tried to sleep through a kicking child can attest. Because ultrasound testing involves bouncing sound waves in order to get a clear picture, movement can give false results either way.
The combination of ultrasound and maternal blood testing increases the odds of early detection to 90% with only 5% erroneous positive results. False positives are maddening, stressful errors in the testing process, and can lead new parents to believe they have a child with Down's Syndrome when, in fact, they don't.
While testing procedures have improved greatly, keep this small chance in mind when looking at test results.
Use of ultrasound and maternal blood testing can help avoid the necessity of the more definitive tests. However, if screening up to this point has indicated a strong possibility of Down's Syndrome in your baby, you may want to go ahead and have the more definitive tests done to get a real, concrete answer.
A high resolution ultrasound scan which is an extremely detailed scan using a very expensive scanner could pick up spina bifida in a baby. In this case, ultrasound becomes a diagnostic test rather than a screening test.
Why need Pre-Natal Pregnant Test by using UltraSound?
An ultrasound is one of the most common prenatal tests, and it is usually performed at least once during the pregnancy. During the ultrasound the doctor will be able to look at your baby's development and check for any health problems or abnormalities. The sex of the baby can also be determined using ultrasound procedures.
Women who are over the age of 35 or who have genetic disorders in their family usually receive amniocentesis as part of their prenatal test routine. During this test, a small amount of the amniotic fluid is collected and analyzed. Any genetic abnormalities or diseases in the baby can be diagnosed through this prenatal test. If there is not enough amniotic fluid present to be collected safely for amniocentesis, or the woman wants test results very early in the pregnancy, than chorionic villus sampling can be used; during this test fetal blood is collected from the umbilical cord. Chorionic villus sampling can also detect addition problems in the fetus such as low oxygen levels or anemia.
Trained sonographers in a medical setting may be able to determine if a fetus is more likely to be born with Down syndrome by observing the thickness or folds of the neck. This is called nuchal translucency thickness.
Some hospitals are beginning to offer “Sequential Screening,” a two-stage test in the first trimester designed to test for Down syndrome, trisomy 18 and other chromosome disorders as well as neural tube defects such as spina bifida without the risk and invasiveness of amniocentesis or chorionic villus sampling (CVS). Participating hospitals may recommend this diagnostic ultrasound to pregnant women over age 35, or to any woman who would like to have the tests. A blood test for hormone levels in the 10th to 14th week is followed up by an ultrasound in which the amount of fluid at the back of the fetus’ neck is observed. The results of the two tests combined reveal “odds” that the fetus is affected with one of the conditions being tested for. A second blood test may be advised between the 15th and 22nd week, at which point the combined results are considered 90-percent accurate in detecting Down syndrome or trisomy 18.
What Would You Do If Your Doctor Said Your Fetus Had a 1 in 6 Chance of Being Born With Down Syndrome?
Since 1983, when doctors noticed that alpha-fetoprotein was usually low in the blood of women who carried a fetus affected with Down syndrome, the search has been on for a test, or combination of tests, that would diagnose the syndrome early in a pregnancy. Women and their partners use this testing so that they can prepare to raise a child who will have profound medical, cognitive, and behavioral challenges, or so that they can end the pregnancy. The best tests now detect up to 95 percent of Down syndrome by combining results from blood tests in the first and second trimesters with an ultrasound examination in the first trimester, and obstetricians across the developed world are screening more of their patients than ever before. None of these tests, however, provide a definitive yes or no answer -- although blood tests that do are in development and may be available as soon as June.
In much of Europe, this increase in screening has coincided with a decrease in the number of babies born with Down syndrome, because many women, armed with this new information, have chosen to terminate these pregnancies. However, many US women -- including Alaska Governor Sarah Palin, whose son with Down syndrome, Trig, was a constant presence on last year's campaign trail -- are finding out their fetuses have the syndrome and are continuing with the pregnancy
At their best, obstetricians provide their patients with information and counseling that empower them to make the right decision -- about testing, and about what to do with the results of these tests. As an obstetrician specializing in complex pregnancies, including those affected by Down syndrome, and try to be informative, supportive, and non-directive, but you can recognize that the options are confusing and the decisions momentous.
