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- What should I do after I have an amniocentesis?
- How does this ultrasound differ from one performed in a Doctor's Office?
- What is a Targeted Ultrasound?
- I have heard that serum screening tests (AFP/triple or quadruple screening) are often wrong. Why do doctors use them?
- Why do I need genetic counseling before amniocentesis?
- Can ultrasound pick up all birth defects?
- My Serum Screening test was abnormal and my doctor is sending me to the ATU. What does this mean?
- What is Down Syndrome?
- What is amniocentesis and what are the risks of the procedure?
- I am 35 years old. What is the chance that my fetus has Down syndrome?
- How can ultrasound be used to screen for Down syndrome in older women?
- What should I do after I have an amniocentesis?
- Relax for the remainder of the day.
- Decrease your activities. Do not engage in strenuous activity, including exercise, housework, heavy lifting, carrying other children, sexual intercourse, or tub bathing.
- Watch for any signs of cramping, vaginal bleeding or discharge of amniotic fluid, or infection (fever, redness at tap site). Please contact us with any questions or problems at 384-3544.
- You may resume your normal activities the following day, as long as you have not had any complications. Your chromosome results will be available in 10 days to 2 weeks.
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- How does this ultrasound differ from one performed in a Doctor's Office?
Your doctor/midwife may have referred you to the Antenatal Testing Unit for a targeted ultrasound. This is performed using state of the art equipment and interpreted by individuals who specialize in ultrasound imaging. Common reasons for Targeted (Level II) Ultrasound include previous or family history of birth defects, abnormal serum screening (AFP, triple or quadruple Screen Testing), advanced maternal age, medication usage during pregnancy, or concerns over the results of an ultrasound performed in your doctor's office.
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- What is a Targeted Ultrasound?
A targeted ultrasound, or Level II ultrasound examination provides a greater assessment of fetal anatomy, using top of the line ultrasound equipment and performed by specialists in prenatal diagnosis. This is recommended for women with personal or family histories of birth defects, medication exposures, abnormal serum screening tests, or advanced maternal age.
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- I have heard that serum screening tests (AFP/triple or quadruple screening) are often wrong. Why do doctors use them?
Serum Screening tests are blood tests that can be easily and safely performed on a large group of women to identify those women whose fetuses may need further testing.
An abnormal screening test does not mean your baby has a birth defect or other problem, but does suggest the need for closer evaluation. On the average, only 1-5% of women with abnormal serum screening have a pregnancy with an increased risk for complications. Further testing may include targeted ultrasound, genetic counseling, amniocentesis, fetal monitoring later in pregnancy, or additional blood screening.
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- Why do I need genetic counseling before amniocentesis?
Genetic Counseling is an opportunity to review you and your partner's family history. This will help determine if there is an increased risk of genetic diseases that may run in your family. This is also an opportunity to best determine the risks involved in your pregnancy and answer any questions you may have concerning the prenatal diagnostic testing that is available. Our philosophy in the Antenatal Testing Unit is that of "non-directive counseling" where we will provide you with the medical and genetic information available to help you come to a personal decision that is appropriate for you.
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- Can ultrasound pick up all birth defects?
Ultrasound can detect many, but not all birth defects. Some birth defects may be difficult to see in the fetus. Some may not appear until the fetus has grown to a certain size. In some birth defects, like Down syndrome, only half of the fetuses will have features that look different from normal babies. Most large studies suggest that ultrasound can pick up over half of the birth defects found at birth and that specialized ultrasound can pick up twice as many birth defects as ultrasounds performed in a doctor's office.
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- My Serum Screening test was abnormal and my doctor is sending me to the ATU. What does this mean?
A Serum screening test (triple or quad screening test) is a blood test that measures the levels of certain proteins and hormones produced by the fetus. These include alpha-fetoprotein (AFP), human chorionic gonadatrophin (HCG), and estriol. The newest variation, known as a Quad screen includes these three proteins and another protein, inhibin, for a total of 4 serum analytes.
The screening tests may be abnormal if the level of AFP is too high. This raises the possibility that the fetus may have an abnormality of its spine, spina bifida. On the average, only 3-5 babies out of 100 whose mothers have a high AFP actually have a birth defect.
The screening test may also suggest an increased risk for Down syndrome. This typically results when your AFP level is low and your HCG level is high. Again, only a small percentage of women who have this result actually have a baby with Down syndrome. The test results predict a chance based upon your age and test results, but on the average only 1 woman in 150 who have an abnormal result actually have a baby with Down syndrome. In this situation, an amniocentesis can tell your baby's chromosome results.
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- What is Down Syndrome?
Down syndrome is the most common chromosomal birth defect. It occurs in approximately 1/700 pregnancies. It results when a fetus possesses three, rather than the usual two, copies of the 21st chromosome. This extra genetic material affects a person's physical and cognitive development. Most people with Down syndrome have some level of mental retardation; however, the level usually falls into the mild to moderate range. Children with Down syndrome learn to sit, walk, talk, play, toilet train and do most other activities - only somewhat later than their peers without Down syndrome. Some couples believe it is very important to know whether their fetus may have Down syndrome as it may affect their decisions to continue the pregnancy or prepare for the birth.
We in the Antenatal Testing Unit acknowledge and respect the different personal beliefs of our patients and help to provide them with the medical information necessary to make the right decisions for them.
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- What is amniocentesis and what are the risks of the procedure?
Amniocentesis is a test, usually performed at 16-20 weeks of pregnancy where a thin needle is inserted into the amniotic sac (bag of waters) to remove a small amount of fluid. This fluid contains fetal cells which can be tested for birth defects, such as chromosomal problems (Down Syndrome) or other birth defects. It is performed under ultrasound guidance and the risks of having a miscarriage from the test are very small. Only 1 in 200 woman who have an amniocentesis would be expected to have a complication from the procedure. Common reasons for having an amniocentesis include advanced maternal age, having an abnormal serum screening test, or seeing a birth defect on ultrasound. Results are generally available in 10-14 days. Over 600 amniocenteses are performed each year in the ATU and our doctors all have over 15 years experience with the procedure.
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- I am 35 years old. What is the chance that my fetus has Down syndrome?
The risks of Down syndrome and many other chromosomal birth defects are based upon age of the mother at delivery. This table gives estimates of the risks of Down syndrome and of any chromosome abnormality based upon a mother's age. Each individual woman's risk may be modified by either her serum screening or targeted ultrasound results.
Approximate Risk of Down Syndrome
Based upon Mother's Age at Delivery
Age Risk
20 1/1220
21 1/1150
22 1/1060
23 1/1000
24 1/950
25 1/890
26 1/840
27 1/800
28 1/760
29 1/720
30 1/680
31 1/650
32 1/560
33 1/450
34 1/350
35 1/270
36 1/210
37 1/165
38 1/130
39 1/100
40 1/70
41 1/50
42 1/40
43 1/30
44 1/25
45 1/20
46 1/15
47 1/12
48 1/9
49 1/7
(Data from Hook et al Journal of the American Medical Association 249:15:2034)
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- How can ultrasound be used to screen for Down syndrome in older women?
Certain features found during an ultrasound are slightly more common in Down syndrome fetuses than in normal fetuses. These features are called ultrasound markers. For example, we know that babies with Down syndrome are slightly shorter than normal babies. Therefore, ultrasound has been used to measure bone lengths in an attempt to identify those fetuses with Down syndrome. However, most babies whose bones are slightly shorter are normal babies, so unfortunately this technique is not very accurate in definitely telling us which babies will have Down syndrome.
Ultrasound Markers that we look for:
- Nuchal thickness (thickness of the skin behind the back of the neck)
- A shortened humerus (upper arm bone)
- Very bright appearing (echogenic) bowel
- A bright heart valve attachment (intracardiac echogenic focus)
- Fluid present in the fetal kidneys (renal pyelectesis)
- A shortened femur (lower leg bone)
- A shortened 5th finger
If ultrasound markers are present, it does not mean that your baby has Down syndrome. It just suggests that the chance of your baby having Down syndrome may be slightly higher than if they were not present. It is not necessarily abnormal or unusual for a normal, healthy baby to have one of these features.
Using ultrasound to look for Down syndrome is not a perfect test. Babies that have Down syndrome may look normal on ultrasound and not have any of these features. If no markers are seen on today's ultrasound, this suggests that your chance of having a fetus with Down syndrome may be lower than your age or screening tests indicate. It does not guarantee that your fetus has normal chromosomes.
If you need to be absolutely certain that the fetus has normal chromosomes, because this might change your decisions about continuing the pregnancy, amniocentesis may be a better test for you. It will give a definitive result in 99% of cases.
Finding an ultrasound marker when your baby is actually normal may add stress and anxiety to your pregnancy. We regret that possibility, and we are working toward the time when doctors can provide definite information without taking the small risk of amniocentesis.
If you have any further questions, we will be glad to discuss these with you after your ultrasound examination. Or you may wish to speak with one of our genetic counselors to discuss Down syndrome, amniocentesis, targeted ultrasound, or serum (blood) screening in more detail.
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