Chorionic villus examination or amniocentesis?
You are confused, which examination do you choose? All there is to know about the two most important tests to discover the chromosomal problems of the fetus - with or without a gene chip (CMA). What are the pros and cons of each examination? Is there really a blood test that can replace amniocentesis?
There are some genetic tests carried out during pregnancy: fetal albumin testing, also called a triple test - a blood test done in 16 to 18 weeks of pregnancy and its sensitivity (the efficacy of the examination) for Down syndrome is approximately 65%; A nuchal translucency examination, which is an ultrasound scan that is conducted in the 11th to 14th week of pregnancy with a sensitivity of approximately 75%; Combining a nuchal translucency test and a biochemical genetic blood test in the first trimester of pregnancy increases the sensitivity of the test to approximately 84%, and the combination of the three genetic tests increases the sensitivity of the test to approximately 92%.
Another genetic test, NIPT, is the fetal DNA scan in the mother’s blood - a blood test that tests the probability of Down syndrome, with a sensitivity greater than 99%, and four additional chromosomes (13, 18, X and Y), with a smaller sensitivity Slightly. The examination framework can be expanded, and specific changes may be tested for some genetic diseases.
It is known that genetic tests do not allow an accurate diagnosis, but it tests the possibility of the syndrome. In addition, the scope of screening in this majority of these tests is limited to Down syndrome and only to four additional chromosomes in the NIPT examination. In contrast, screening of placental villi and amniocentesis are diagnostic scans, and address a broader set of chromosomal and genetic problems in the fetus.
Chorionic villus testing and amniocentesis are diagnostic invasive tests to examine all 23 pairs of chromosomes. Through these tests, it is possible to know whether the number of chromosomes is correct, whether there is an excess of chromosomes, which indicates Down syndrome, a shortage of chromosomes, a deficiency, an excess or a change in the location of the genetic material on the chromosomes and others.
In recent years, these two tests have also included examination of the genetic chip, which is an expanded examination that examines the sequence of genetic material in the fetus, allowing the possibility of discovering many syndromes and diseases. Genetic chip testing can only be performed within the framework of chorionic villus or amniotic examination.
Today it is advised to perform a genetic wafer examination in each chorionic villus or amniotic examination; In some places, the genetic wafer examination is performed from the start instead of the usual chromosome examination. Genetic chip testing includes almost everything that is examined within the framework of regular chromosome examination.
Screening for placental villi is performed more early, in the 10 and a half weeks to 14 weeks of pregnancy, while amniocentesis is carried out in the 16th to 22nd weeks of pregnancy. In examining the chorionic villus, cells are taken from the placenta itself, which reflects an image of the cells of the fetus; On the other hand, in the amniocentesis examination, the amniotic fluid itself, which the fetal cells float, is aspirated.
Amniocentesis is performed by inserting a thin needle through the abdomen into the amniotic sac by directing the abdominal ultrasound. Alternatively, screening of chorionic villus can be done in two ways.
The first is similar to the way amniocentesis is performed, but with a thicker needle it is inserted through the abdomen into the placenta itself.
The second method of performing chorionic villus screening is a vaginal method, which is also performed under the guidance of the ventral abdominal waves: insertion of a thin tube into the cervix and from there to the placenta for the extraction of cells. Before performing the examination in this way, the urinary bladder must be full.
For screening of placental villi there is a significant advantage over amniocentesis - in terms of the early stage in which it is performed. If the results of the examination show that the pregnancy must be stopped (God forbid), this can be done at this stage by endometriosis, while stopping the pregnancy at a later stage, after the amniocentesis is performed, is a more complicated process and often involves greater risks and Greater psychological and sensory crises.
One of the disadvantages of screening placental villi is that it is a more expensive examination than amniocentesis and is available less frequently because its procedure requires high skills in terms of the laboratory and the doctor performing, and in the country, there are few doctors who are qualified to do the examination and who have the skills to do it.
In terms of risks, previously, screening of chorionic villi was considered a cause of early miscarriage, but no significant statistical difference was found in studies conducted in recent years in terms of severity of the two tests, and it can be said that the extent of risk in both tests today is similar.
Minor pain may appear due to contractions.
After the two exams, minor pain due to contractions, similar to menstrual pain, may appear, but these pain disappear after a few hours have passed. After a vaginal villus examination, a slight bleeding may appear for a few days.It is a good idea to take a two-day break after performing the two tests. It is not necessary to lie down in bed, but it is advisable not to do any strenuous activities.
Risks are similar in both tests: infection, miscarriage, divorced, and amniocentesis. The risk of one of these risks is low, but an examination should be performed immediately when one of the following symptoms appears: severe bleeding after screening of the vaginal placental villi; General bleeding, after examination of amniotic fluid or abdominal placenta villi; Temperature rise to 38 degrees or more; Severe pain or amniocentesis.
Amniocentesis and chorionic villus testing are provided within the basket of health services for women who meet the following criteria:
Over the age of 35.
Women who had previously been diagnosed with chromosomal or genetic problems.
Women whose husbands carry a genetic disease.
Women whose genetic testing indicated a significant risk.
Women whose ultrasound examinations indicated a significant risk.
As we mentioned, most of the time, since screening of chorionic villi is more expensive and requires higher medical skills, the woman is referred to perform amniocentesis.
A NIPT examination is a highly sensitive examination, but it is a genetic, not a diagnostic examination. For this reason, this test cannot replace the amniocentesis test. Likewise, a genetic wafer assay cannot be performed in a NIPT assay. Compared to other genetic tests, NIPT is more sensitive. However, it must be remembered: a more accurate medical diagnosis is performed by examining the amniotic fluid or screening the placental villi.
Dr.. Yusuf Har Touf is a obstetrician and gynecologist, deputy director of the ultrasound unit at Tel Aviv Medical Center (Liss Hospital).
Chorionic villus examination or amniocentesis?
Chromosomal problems in the fetus can be discovered with genetic or diagnostic tests. Genetic tests available today to discover chromosomal problems in the fetus address Down syndrome and a syndrome called trisomy 18 (trisomy) only, and it does not accurately diagnose the condition, but rather examines the possibility of having one of these syndromes in the fetus.There are some genetic tests carried out during pregnancy: fetal albumin testing, also called a triple test - a blood test done in 16 to 18 weeks of pregnancy and its sensitivity (the efficacy of the examination) for Down syndrome is approximately 65%; A nuchal translucency examination, which is an ultrasound scan that is conducted in the 11th to 14th week of pregnancy with a sensitivity of approximately 75%; Combining a nuchal translucency test and a biochemical genetic blood test in the first trimester of pregnancy increases the sensitivity of the test to approximately 84%, and the combination of the three genetic tests increases the sensitivity of the test to approximately 92%.
It addresses a broader set of chromosomal and genetic problems in the fetus.
Another genetic test, NIPT, is the fetal DNA scan in the mother’s blood - a blood test that tests the probability of Down syndrome, with a sensitivity greater than 99%, and four additional chromosomes (13, 18, X and Y), with a smaller sensitivity Slightly. The examination framework can be expanded, and specific changes may be tested for some genetic diseases.
It is known that genetic tests do not allow an accurate diagnosis, but it tests the possibility of the syndrome. In addition, the scope of screening in this majority of these tests is limited to Down syndrome and only to four additional chromosomes in the NIPT examination. In contrast, screening of placental villi and amniocentesis are diagnostic scans, and address a broader set of chromosomal and genetic problems in the fetus.
What is chorionic villus screening and amniocentesis?
Chorionic villus testing and amniocentesis are diagnostic invasive tests to examine all 23 pairs of chromosomes. Through these tests, it is possible to know whether the number of chromosomes is correct, whether there is an excess of chromosomes, which indicates Down syndrome, a shortage of chromosomes, a deficiency, an excess or a change in the location of the genetic material on the chromosomes and others.
In recent years, these two tests have also included examination of the genetic chip, which is an expanded examination that examines the sequence of genetic material in the fetus, allowing the possibility of discovering many syndromes and diseases. Genetic chip testing can only be performed within the framework of chorionic villus or amniotic examination.
Today it is advised to perform a genetic wafer examination in each chorionic villus or amniotic examination; In some places, the genetic wafer examination is performed from the start instead of the usual chromosome examination. Genetic chip testing includes almost everything that is examined within the framework of regular chromosome examination.
What are the differences between chorionic villus and amniocentesis?
Screening for placental villi is performed more early, in the 10 and a half weeks to 14 weeks of pregnancy, while amniocentesis is carried out in the 16th to 22nd weeks of pregnancy. In examining the chorionic villus, cells are taken from the placenta itself, which reflects an image of the cells of the fetus; On the other hand, in the amniocentesis examination, the amniotic fluid itself, which the fetal cells float, is aspirated.
Amniocentesis is performed by inserting a thin needle through the abdomen into the amniotic sac by directing the abdominal ultrasound. Alternatively, screening of chorionic villus can be done in two ways.
The first is similar to the way amniocentesis is performed, but with a thicker needle it is inserted through the abdomen into the placenta itself.
The second method of performing chorionic villus screening is a vaginal method, which is also performed under the guidance of the ventral abdominal waves: insertion of a thin tube into the cervix and from there to the placenta for the extraction of cells. Before performing the examination in this way, the urinary bladder must be full.
What are the pros and cons of each examination?
For screening of placental villi there is a significant advantage over amniocentesis - in terms of the early stage in which it is performed. If the results of the examination show that the pregnancy must be stopped (God forbid), this can be done at this stage by endometriosis, while stopping the pregnancy at a later stage, after the amniocentesis is performed, is a more complicated process and often involves greater risks and Greater psychological and sensory crises.
One of the disadvantages of screening placental villi is that it is a more expensive examination than amniocentesis and is available less frequently because its procedure requires high skills in terms of the laboratory and the doctor performing, and in the country, there are few doctors who are qualified to do the examination and who have the skills to do it.
In terms of risks, previously, screening of chorionic villi was considered a cause of early miscarriage, but no significant statistical difference was found in studies conducted in recent years in terms of severity of the two tests, and it can be said that the extent of risk in both tests today is similar.
Minor pain may appear due to contractions.
Are there any side effects for the tests?
After the two exams, minor pain due to contractions, similar to menstrual pain, may appear, but these pain disappear after a few hours have passed. After a vaginal villus examination, a slight bleeding may appear for a few days.It is a good idea to take a two-day break after performing the two tests. It is not necessary to lie down in bed, but it is advisable not to do any strenuous activities.
What are the risks involved in the tests?
Risks are similar in both tests: infection, miscarriage, divorced, and amniocentesis. The risk of one of these risks is low, but an examination should be performed immediately when one of the following symptoms appears: severe bleeding after screening of the vaginal placental villi; General bleeding, after examination of amniotic fluid or abdominal placenta villi; Temperature rise to 38 degrees or more; Severe pain or amniocentesis.
What are the criteria that enable examinations to be carried out in the basket of health services?
Amniocentesis and chorionic villus testing are provided within the basket of health services for women who meet the following criteria:
Over the age of 35.
Women who had previously been diagnosed with chromosomal or genetic problems.
Women whose husbands carry a genetic disease.
Women whose genetic testing indicated a significant risk.
Women whose ultrasound examinations indicated a significant risk.
As we mentioned, most of the time, since screening of chorionic villi is more expensive and requires higher medical skills, the woman is referred to perform amniocentesis.
Can NIPT test replace amniocentesis?
A NIPT examination is a highly sensitive examination, but it is a genetic, not a diagnostic examination. For this reason, this test cannot replace the amniocentesis test. Likewise, a genetic wafer assay cannot be performed in a NIPT assay. Compared to other genetic tests, NIPT is more sensitive. However, it must be remembered: a more accurate medical diagnosis is performed by examining the amniotic fluid or screening the placental villi.
Summary
Amniocentesis and chorionic villus examination are invasive diagnostic tests, which are performed to detect chromosomal and genetic problems, such as Down syndrome. The differences between the two tests primarily lie in the stages of pregnancy in which the two tests can be performed (screening of placental villi in the 10 and a half weeks to 14 weeks of pregnancy; amniocentesis in week 16 to 22 of pregnancy), in the manner in which they are performed and their availability. The risks involved in both tests are minimal and are similar for both tests. There are additional genetic tests to discover chromosomal problems and some genetic diseases in the fetus, including a blood test called NIPT. However, no genetic examination can replace the amniocentesis or chorionic villus examination, because these tests are not a diagnosis but only an estimate of severity and only specific signs or diseases.
Dr.. Yusuf Har Touf is a obstetrician and gynecologist, deputy director of the ultrasound unit at Tel Aviv Medical Center (Liss Hospital).
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