Genetic testing, of any sort, usually brings a large debate. The alphfetoprotein (AFP) or triple screen are no exceptions.
The AFP test, sometimes called the MSAFP or maternal serum AFP, is where a blood sample is drawn from the mother to check the levels of AFP. AFP is a protein secreted by the fetal liver and excreted in the mother's blood. It is generally used for detecting neural tube defects, but it can also indicate: abdominal wall defects esophageal and duodenal atresia, some renal and urinary tract anomalies turner syndrome, some low birth weight fetuses, and placental complications. A low level of AFP could also indicate Down Syndrome.
The triple screen measures not only AFP, but hCG and estriol as well. This test is more accurate and screens for additional genetic problems, and is beginning to replace the standard AFP. Generally speaking, any combination of the testing will identify 60% of the babies with Down Syndrome and 80-90% of the babies with neural tube defects..
The controversy in these tests lies in many places. One of which is the accuracy of the screenings. While some claim that they have only a 5% "false positive" rate, most research finds that there are 80+% rate of positive tests while the baby is unaffected. The false positive rates depend on many factors, including appropriate gestational age, maternal age, weight and the presence of diabetes.
False positives may not seem like a problem, however, there are follow up tests that are done that do carry risks, like amniocentesis, which does carry a 1 - 2% rate of fetal loss. The standard is usually to repeat the AFP or triple screen. Another positive screen will then go to the Level II Ultrasound. Ultrasound can even be used to detect some of the anomalies associated with Downs Syndrome. If the ultrasound doesn't find a mix up in gestational age, or a multiple pregnancy, an amniocentesis is generally the next step.
There is a possible benefit of identifying neural tube defects before birth, because that can alter care. Such as the mode of delivery. It is generally considered safer for a baby with spina bifida to have a cesarean delivery. Although this can also be identified by ultrasound alone.
It has been estimated that every positive screening will cost approximately $106,000.
Of the positive test results, 90% of these babies will not have any anomalies. There may be other benign reasons for the elevated or low levels of the hormones, specifically the gestational age, or multiple pregnancies. The AFP test is generally done between the 16th and 18th weeks of pregnancy, while the triple screen can be done a bit earlier. The gestational age is very important, because the amount of hormone in your blood will vary with gestational age.
The American College of Obstetricians and Gynecologists have stated that they believe this test should be offered to all pregnant women, regardless of maternal age. However, many women are made to believe the testing is mandatory. Many who refuse are asked to sign waivers in order to not take the test. While others are finding that their insurance coverage has a part to play in the whole scenario.
The test results are generally given as either positive/negative or a risk ranking, such as: 1/47 chance of having a baby with X anomaly. As well as low/high rankings. It is important to remember that being at an increased risk does not mean your baby has the defect. You should also ask that your practitioner explain the results in detail to you.
Physician-researchers at Boston's Brigham and Women's Hospital, after studying 87,584 pregnancies, reported that an elevated AFP [alpha-feto-protein] level in conjunction with a normal ultrasound scan implies a less than 0.1 percent chance that the baby will have one of the four most common birth defects. In light of the finding that amniocentesis itself carries a 0.5 to 1.5 percent chance of terminating a pregnancy (Robin J.R. Blatt, Prenatal Tests), the researchers have concluded that "many women may choose not to have an amniocentesis when informed that the risk of pregnancy loss is substantially greater than the likelihood of finding an anomaly". (New England Journal of Medicine 323, No. 9, Aug 30, 1990)
Whether or not to have the test is a very hard decision and a very personal one. Some women feel that no matter what is wrong that they would not terminate the pregnancy, and therefore do not want the test. While others are very happy to have the normal results, even knowing that there are no guarantees.
The AFP test, sometimes called the MSAFP or maternal serum AFP, is where a blood sample is drawn from the mother to check the levels of AFP. AFP is a protein secreted by the fetal liver and excreted in the mother's blood. It is generally used for detecting neural tube defects, but it can also indicate: abdominal wall defects esophageal and duodenal atresia, some renal and urinary tract anomalies turner syndrome, some low birth weight fetuses, and placental complications. A low level of AFP could also indicate Down Syndrome.
The triple screen measures not only AFP, but hCG and estriol as well. This test is more accurate and screens for additional genetic problems, and is beginning to replace the standard AFP. Generally speaking, any combination of the testing will identify 60% of the babies with Down Syndrome and 80-90% of the babies with neural tube defects..
The controversy in these tests lies in many places. One of which is the accuracy of the screenings. While some claim that they have only a 5% "false positive" rate, most research finds that there are 80+% rate of positive tests while the baby is unaffected. The false positive rates depend on many factors, including appropriate gestational age, maternal age, weight and the presence of diabetes.
False positives may not seem like a problem, however, there are follow up tests that are done that do carry risks, like amniocentesis, which does carry a 1 - 2% rate of fetal loss. The standard is usually to repeat the AFP or triple screen. Another positive screen will then go to the Level II Ultrasound. Ultrasound can even be used to detect some of the anomalies associated with Downs Syndrome. If the ultrasound doesn't find a mix up in gestational age, or a multiple pregnancy, an amniocentesis is generally the next step.
There is a possible benefit of identifying neural tube defects before birth, because that can alter care. Such as the mode of delivery. It is generally considered safer for a baby with spina bifida to have a cesarean delivery. Although this can also be identified by ultrasound alone.
It has been estimated that every positive screening will cost approximately $106,000.
Of the positive test results, 90% of these babies will not have any anomalies. There may be other benign reasons for the elevated or low levels of the hormones, specifically the gestational age, or multiple pregnancies. The AFP test is generally done between the 16th and 18th weeks of pregnancy, while the triple screen can be done a bit earlier. The gestational age is very important, because the amount of hormone in your blood will vary with gestational age.
The American College of Obstetricians and Gynecologists have stated that they believe this test should be offered to all pregnant women, regardless of maternal age. However, many women are made to believe the testing is mandatory. Many who refuse are asked to sign waivers in order to not take the test. While others are finding that their insurance coverage has a part to play in the whole scenario.
The test results are generally given as either positive/negative or a risk ranking, such as: 1/47 chance of having a baby with X anomaly. As well as low/high rankings. It is important to remember that being at an increased risk does not mean your baby has the defect. You should also ask that your practitioner explain the results in detail to you.
Physician-researchers at Boston's Brigham and Women's Hospital, after studying 87,584 pregnancies, reported that an elevated AFP [alpha-feto-protein] level in conjunction with a normal ultrasound scan implies a less than 0.1 percent chance that the baby will have one of the four most common birth defects. In light of the finding that amniocentesis itself carries a 0.5 to 1.5 percent chance of terminating a pregnancy (Robin J.R. Blatt, Prenatal Tests), the researchers have concluded that "many women may choose not to have an amniocentesis when informed that the risk of pregnancy loss is substantially greater than the likelihood of finding an anomaly". (New England Journal of Medicine 323, No. 9, Aug 30, 1990)
Whether or not to have the test is a very hard decision and a very personal one. Some women feel that no matter what is wrong that they would not terminate the pregnancy, and therefore do not want the test. While others are very happy to have the normal results, even knowing that there are no guarantees.
