|Many doctors have been asked the question, “Doctor, is my baby normal?”
The physician replying to the above question must remember that all medical diagnostic tests should be performed only in order to identify and, if possible, cure or ameliorate whatever condition the patient may be suffering from. He or she should also know that some currently used medical diagnostic tests are so dangerous to the patient or to her unborn child that they should rarely be used – and some should not be used at all.
These principles apply in the case where it is proposed that a pregnant woman should have an amniocentesis test and-or a chorionic villus sampling (CVS) test. Situations where amniocentesis is justified are rare. Some examples are:
1) To learn if the lungs of an unborn baby are mature enough, where early delivery is needed, to protect the life or health of the mother or baby.
2) To determine if there is uterine infection associated with ruptured membranes
3) To determine if an unborn baby has one of two extremely rare diseases of body chemistry where ante-natal treatment would result in the birth of a healthy baby. These conditions are biotin dependence and methylmalonic acidemia
Situations where amniocentesis is not justified are common. In most instances, amniocentesis does not help the baby and in one in 200 cases, it results in miscarriage with death of the child, whether he or she is “normal” or not. In these instances, amniocentesis is not justified morally. Amniocentesis is typically offered when it is suspected that the fetus may have Down syndrome, cystic fibrosis, Tay Sachs disease or Huntington disease. If the diagnosis is positive, these babies are often aborted. Experimental prenatal surgery for spina bifida, so far, has not shown certain benefit to the baby and creates an increased risk to the child and the mother.
Except in the diagnosis of congenital adrenal hyperplasia, CVS is performed if the fetus is expected to have a disease due to chromosomal abnormality; that is, Down syndrome, or an abnormality due to an inheritable genetic disorder – Tay Sachs or cystic fibrosis – that CVS cannot cure or ameliorate. It is, therefore, not morally justified.
Up to the present, physicians have recommended amniocentesis only to women who were 35 years of age or older. Earlier this year, the American College of Obstetricians and Gynecologists advised that all pregnant women, regardless of age, should be offered the option of diagnostic testing for Down syndrome before the 20th week of pregnancy. There are two preliminary tests that do not harm the fetus. One is ultrasound screening that measures the tissue translucency at the back of the neck of the fetus that occurs in Down syndrome. The second is blood tests that measure the human chorionic gonadotropin and pregnancy-associated plasma proteins. Mothers found by these early tests to have an increased risk of having a baby with Down syndrome should, the ACOG states, be offered amniocentesis or CVS. If those tests should be found to be positive, the patient should be offered genetic counselling.
Note the following data provided in the ACOG news release:
• The ultrasound test’s “pick up,” probably better called sensitivity (its ability to correctly identify a given disease), is claimed to be 75 per cent for Down syndrome
• The blood test’s “pick up” (sensitivity) is 60 per cent
• The “pick up” (sensitivity) if both tests are used, is claimed to be 90 per cent
• The ACOG news release gave no explicit indication of the specificity of these tests, (their ability to exclude false positive diagnoses)
The ACOG news release on Jan. 4, 2007 claimed that “higher sensitivity or detection rates (defined as a percentage of Down syndrome pregnancies identified with a positive test result) at low positive rates have led to increased use of screening and a decline in the number of amniocenteses performed.” This decline, however, is in relation to the absolute number of procedures. That absolute number will be increased if all the women are offered the preliminary tests. The decline in the number of amniocenteses in relation to the number of diagnostic procedures done in comparison with previous practice is offset by the large increase in procedures done because amniocentesis is now offered to all pregnant women. When more are tested, the prevalence of Down syndrome falls and this results in a higher false positive rate of diagnosis.
CVS is usually performed between 10 and 12 weeks’ gestation and carries a one in 100 risk of miscarriage as a direct result of the test. Amniocentesis is usually carried out at 14 to 18 weeks and carries a risk of miscarriage of one in 200. If done before 14 weeks, the risk is greater.
Patients should be told that the rate of occurrence of Down syndrome in pregnant women between 15 and 19 years old is 1/1,250. At 20 to 24 years old, it is 1/1,400. At age 25 to 29 years, it is 1/1,100. At age 30 to 31, 1/900 and at age 35, it is 1/350.
Since the occurrence rate of Down syndrome in women less than 35 years of age is low, the number of false positive diagnoses resulting from the preliminary tests recommended by the ACOG (the ultrasound and blood tests) will tend to be high.
These tests do not, in themselves, precipitate miscarriage and in this sense, are regarded as “safe.” However, if such a “safe” test resulted in a false positive diagnosis of Down syndrome, a woman who originally may have had no intention of having an abortion, might choose to have the confirmatory tests of CVS and amniocentesis that are associated with a high rate of miscarriage precipitated by the test itself, whether the baby is “normal” or not.
Furthermore, the ACOG, and the medical profession as a whole, emphasize that the ultrasound test is not reliable when done by a centre, or individuals, that do not meet the criteria for specific training, standardization, use of appropriate ultrasound equipment and ongoing quality assessment. How many clinics offer this standard of care is probably unknown.
Amniocentesis should not be performed unless there is, as is rarely the case, sufficient reason as described above. CVS should never be performed, because the diseases it reveals are incurable and because it is associated with such a high rate of miscarriage. The estimates of how many diagnoses will prove to be a false positive or a false negative based on the diagnostic ultrasound screening and the blood tests recommended by the ACOG are not relevant to women less than 35 years old. Estimates based on demonstration of the presence of aneuploidy by prenatal karyotype following amniocentesis and-or CVS are more accurate. All of these estimates, no matter how accurate, however, are irrelevant to the moral argument about prenatal diagnosis.
In almost all cases, these are tests intended to show the presence of a disease that cannot be cured. The only “therapy” offered is abortion of the child. Amniocentesis, and in some cases CVS, diagnoses a “normal” pre-born child as having a disorder when, in fact, the child is normal. These tests also, in and of themselves, probably directly cause the death of more unborn children, both “normal” and “abnormal,” than does deliberate abortion of those diagnosed as having prenatal disease.
In spite of these facts, many physicians persist in offering these tests. They rationalize their activities by saying that, now that there are safe early tests, it is ethical to offer all pregnant women the full panoply of choices that women 35 years of age or older have been offered since the 1970s. In 2004, 337,000 babies were born in Canada. If all of those mothers had amniocentesis and CVS, up to 3,370 babies might have been aborted, most of them “normal.” To abort children, or to carry out diagnostic tests that are meant, or are likely to, lead to their abortion, just because they may be disabled or a burden to others, is to deny them the spiritual human dignity that is the basis of their human rights and the human rights of all.
Dr. John B. Shea is the medical adviser for Campaign Life Coalition and a member of the editorial board of Catholic Insight. This article originally appeared atwww.catholicinsight.com.