Prenatal Diagnosis of Genetic Disorders
"Will my baby be normal?" That's the question all parents ask, and some with good reason. Knowing the family history of both you and your baby's father will allow us to anticipate certain problems that can be minimized with proper care. Today, we have a better chance of diagnosing certain genetically transmitted diseases thanks to medical technology.
Maternal Serum Alpha-Fetoprotein (AFP) Test
Special tests can provide additional information about the development and well-being of the fetus. You probably will not have all the tests described here. Each pregnancy is different and your clinician will discuss with you the test or tests most appropriate for your pregnancy.
The Maternal serum alphafetoprotein (AFP) test screens for:
* Open neural tube defects, which include spine bifida (open spine) and anencephaly (absent brain)
* Down Syndrome, a chromosomal abnormality associated with mental retardation, developmental delays, and physical problems
* Potentially high-risk pregnancies that should be followed closely in the third trimester
The test measures pregnancy-related proteins in the mother's blood and is best performed at 16 to 18 weeks of pregnancy. The AFP requires only a small blood sample from the mother's arm. There is no risk to the fetus. Remember, this is only a screening test, which flags pregnancies that may need follow-up tests. It will not catch all fetuses with the above problems.
An abnormal AFP level does not always mean the fetus has a birth defect. The pregnancy may be more or less advanced than estimated, or about to miscarry. Levels are higher in pregnancies with more than one fetus. Abnormal results occur in roughly 10 out of every 100 women tested who will be under age 35 at delivery. Women 35 are more likely to have abnormal results because the risk of Down syndrome increases with age.
Because the AFP is a screening test, some women will be identified as being at increased risk even though they are carrying normal fetuses. In fact, most women with abnormal AFP test results will have normal babies (about 96% or 24 out of 25). To follow up an abnormal AFP, your clinician will probably suggest a repeat blood test, ultrasound, or amniocentesis. If follow-up tests confirm a birth defect, your clinician may refer you to a medical geneticist or other specialists. They can help you better understand the birth defect and its implications. An AFP is generally recommended for all pregnant women. However, whether or not you have an AFP is up to you. If you are interested in having this test, discuss it with your clinician.
Amniocentesis
Clinicians most commonly use amniocentesis to detect or confirm chromosomal abnormalities, such as Down syndrome, and open neural tube defects. In special cases, it may test for other genetic disorders such as sickle cell anemia or Tay Sachs disease. Amniocentesis cannot identify structural problems such as cleft palate or heart defects.
A woman may be offered amniocentesis if:
* she will be 35 (or older) at delivery
* she had an abnormal AFP result
* either parent of the pregnancy has a known chromosomal abnormality a chromosomal abnormality affected previous pregnancy (for example, Down syndrome)
* either parent of the pregnancy has a strong family history of chromosome ,abnormalities, genetic disease, or open spine defects
Amniocentesis is usually performed between 15 and 17 weeks of pregnancy, sometimes earlier. During this test, the clinician places a thin needle through the abdominal wall and into the uterus. He or she withdraws a small amount of amniotic fluid. Ultrasound helps the clinician select a safe spot to insert the needle. The fluid contains fetal cells, which are tested in a laboratory. The tests can determine the fetus' chromosomal makeup, AFP level, and sex. Usually, amniocentesis is not painful, but may be slightly uncomfortable. Cramping sometimes follows the procedure.
Amniocentesis is a safe procedure. As with most tests, however, there is some risk involved. The most serious is miscarriage, estimated at less than 1%. When the mother is over age 35, the risks of possible chromosomal abnormalities begin to outweigh the risk of miscarriage caused by amniocentesis. The risk of injury to the fetus is extremely small. Some couples would choose to carry the pregnancy to term regardless of the test results. In this case, amniocentesis may not be worth the risks.
If you are interested in amniocentesis, talk with your clinician. S/he can advise you about the risks and benefits, but the decision is yours. Genetic counseling is available for parents who would like more help understanding the procedure and the possible test results.
Chorionic villi sampling (CVS)
CVS can detect genetic disorders and chromosomal abnormalities earlier in pregnancy than amniocentesis. CVS cannot screen for open neural tube defects. (However, a woman can have an AFP test to screen for neural tube defects).
A woman might consider CVS if:
* she will be 40 (or older) at delivery
* parent of the pregnancy has a known chromosomal abnormality
* a chromosomal abnormality affected a previous pregnancy (for example, Down syndrome)
* either parent of the pregnancy has a strong family history of chromosomal abnormalities or certain genetic disorders CVS is usually performed between nine and 11 weeks of pregnancy.
During this test, a clinician inserts a thin plastic tube through the vagina and cervix and into the uterine cavity. S/he withdraws a small piece of the tissue that will develop into the placenta. As with amniocentesis, ultrasound helps guide the procedure. Chromosome analysis is done on cells from the tissue sample.
This prenatal test has been available in the United States only since 1983 and clinicians are still evaluating its safety and accuracy. There are some serious drawbacks to CVS. Test results may be difficult to interpret and the risk of miscarriage is roughly twice that for amniocentesis. Also, there is a small risk that the mother might develop an infection in the uterus. And some recent studies link CVS with limb defects. Some couples would choose to carry the pregnancy to term regardless of the test results. For them, CVS may not be worth the risks.
Whether or not you should have CVS is a personal decision. Genetic counseling is available for parents who want to learn more about the test and possible results. If you are interested in CVS, talk with your clinician.
Glucose Tolerance Test for Gestational Diabetes
Clinicians routinely screen pregnant women for sugar (glucose) intolerance between the 24th and 30th week of pregnancy. Pregnancy can change the way your body processes sugar. Some women develop pregnancy-related diabetes called gestational diabetes. Early detection, with changes in diet (and for some women, insulin), can help prevent problems associated with this condition.
For this screening, you drink a sweet liquid at the laboratory and have a blood sample taken one hour later. (Do not consume sugary foods or drinks before any blood sugar tests. This can confuse the results.) An abnormal result on this screening test does not always mean you have gestational diabetes. A follow-up test is necessary to confirm whether you actually have a sugar intolerance.
source : www.womanhealth.net
"Will my baby be normal?" That's the question all parents ask, and some with good reason. Knowing the family history of both you and your baby's father will allow us to anticipate certain problems that can be minimized with proper care. Today, we have a better chance of diagnosing certain genetically transmitted diseases thanks to medical technology.
Maternal Serum Alpha-Fetoprotein (AFP) Test
Special tests can provide additional information about the development and well-being of the fetus. You probably will not have all the tests described here. Each pregnancy is different and your clinician will discuss with you the test or tests most appropriate for your pregnancy.
The Maternal serum alphafetoprotein (AFP) test screens for:
* Open neural tube defects, which include spine bifida (open spine) and anencephaly (absent brain)
* Down Syndrome, a chromosomal abnormality associated with mental retardation, developmental delays, and physical problems
* Potentially high-risk pregnancies that should be followed closely in the third trimester
The test measures pregnancy-related proteins in the mother's blood and is best performed at 16 to 18 weeks of pregnancy. The AFP requires only a small blood sample from the mother's arm. There is no risk to the fetus. Remember, this is only a screening test, which flags pregnancies that may need follow-up tests. It will not catch all fetuses with the above problems.
An abnormal AFP level does not always mean the fetus has a birth defect. The pregnancy may be more or less advanced than estimated, or about to miscarry. Levels are higher in pregnancies with more than one fetus. Abnormal results occur in roughly 10 out of every 100 women tested who will be under age 35 at delivery. Women 35 are more likely to have abnormal results because the risk of Down syndrome increases with age.
Because the AFP is a screening test, some women will be identified as being at increased risk even though they are carrying normal fetuses. In fact, most women with abnormal AFP test results will have normal babies (about 96% or 24 out of 25). To follow up an abnormal AFP, your clinician will probably suggest a repeat blood test, ultrasound, or amniocentesis. If follow-up tests confirm a birth defect, your clinician may refer you to a medical geneticist or other specialists. They can help you better understand the birth defect and its implications. An AFP is generally recommended for all pregnant women. However, whether or not you have an AFP is up to you. If you are interested in having this test, discuss it with your clinician.
Amniocentesis
Clinicians most commonly use amniocentesis to detect or confirm chromosomal abnormalities, such as Down syndrome, and open neural tube defects. In special cases, it may test for other genetic disorders such as sickle cell anemia or Tay Sachs disease. Amniocentesis cannot identify structural problems such as cleft palate or heart defects.
A woman may be offered amniocentesis if:
* she will be 35 (or older) at delivery
* she had an abnormal AFP result
* either parent of the pregnancy has a known chromosomal abnormality a chromosomal abnormality affected previous pregnancy (for example, Down syndrome)
* either parent of the pregnancy has a strong family history of chromosome ,abnormalities, genetic disease, or open spine defects
Amniocentesis is usually performed between 15 and 17 weeks of pregnancy, sometimes earlier. During this test, the clinician places a thin needle through the abdominal wall and into the uterus. He or she withdraws a small amount of amniotic fluid. Ultrasound helps the clinician select a safe spot to insert the needle. The fluid contains fetal cells, which are tested in a laboratory. The tests can determine the fetus' chromosomal makeup, AFP level, and sex. Usually, amniocentesis is not painful, but may be slightly uncomfortable. Cramping sometimes follows the procedure.
Amniocentesis is a safe procedure. As with most tests, however, there is some risk involved. The most serious is miscarriage, estimated at less than 1%. When the mother is over age 35, the risks of possible chromosomal abnormalities begin to outweigh the risk of miscarriage caused by amniocentesis. The risk of injury to the fetus is extremely small. Some couples would choose to carry the pregnancy to term regardless of the test results. In this case, amniocentesis may not be worth the risks.
If you are interested in amniocentesis, talk with your clinician. S/he can advise you about the risks and benefits, but the decision is yours. Genetic counseling is available for parents who would like more help understanding the procedure and the possible test results.
Chorionic villi sampling (CVS)
CVS can detect genetic disorders and chromosomal abnormalities earlier in pregnancy than amniocentesis. CVS cannot screen for open neural tube defects. (However, a woman can have an AFP test to screen for neural tube defects).
A woman might consider CVS if:
* she will be 40 (or older) at delivery
* parent of the pregnancy has a known chromosomal abnormality
* a chromosomal abnormality affected a previous pregnancy (for example, Down syndrome)
* either parent of the pregnancy has a strong family history of chromosomal abnormalities or certain genetic disorders CVS is usually performed between nine and 11 weeks of pregnancy.
During this test, a clinician inserts a thin plastic tube through the vagina and cervix and into the uterine cavity. S/he withdraws a small piece of the tissue that will develop into the placenta. As with amniocentesis, ultrasound helps guide the procedure. Chromosome analysis is done on cells from the tissue sample.
This prenatal test has been available in the United States only since 1983 and clinicians are still evaluating its safety and accuracy. There are some serious drawbacks to CVS. Test results may be difficult to interpret and the risk of miscarriage is roughly twice that for amniocentesis. Also, there is a small risk that the mother might develop an infection in the uterus. And some recent studies link CVS with limb defects. Some couples would choose to carry the pregnancy to term regardless of the test results. For them, CVS may not be worth the risks.
Whether or not you should have CVS is a personal decision. Genetic counseling is available for parents who want to learn more about the test and possible results. If you are interested in CVS, talk with your clinician.
Glucose Tolerance Test for Gestational Diabetes
Clinicians routinely screen pregnant women for sugar (glucose) intolerance between the 24th and 30th week of pregnancy. Pregnancy can change the way your body processes sugar. Some women develop pregnancy-related diabetes called gestational diabetes. Early detection, with changes in diet (and for some women, insulin), can help prevent problems associated with this condition.
For this screening, you drink a sweet liquid at the laboratory and have a blood sample taken one hour later. (Do not consume sugary foods or drinks before any blood sugar tests. This can confuse the results.) An abnormal result on this screening test does not always mean you have gestational diabetes. A follow-up test is necessary to confirm whether you actually have a sugar intolerance.
source : www.womanhealth.net
No comments:
Post a Comment