E5. Prenatal Diagnosis of Genetic Disease

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A Cross-Cultural Introduction to Bioethics

E5. Prenatal Diagnosis of Genetic Disease

Chapter objectives

Genetic disease affects many persons, and in cases where it is severe, some families decide not to have children. For many parents they only realize this after the birth of the first affected child. Prenatal diagnosis allows the conditions of the embryo or fetus to be checked prior to birth, which presents several options to parents.

This chapter aims to:

1. Describe methods for prenatal diagnosis.

2. Highlight major bioethical concerns associated with the choices that can be made.

3. Emphasize that the state should never force selective abortions because of prenatal diagnosis and discuss the ethical limits of parental choice.

E5.1. Prenatal screening

Prenatal diagnosis or screening has become associated with normal prenatal care in most industrialised countries. There are some important non-genetic screening programmes. For example, if a woman is not immune to rubella, she should be immunised before becoming pregnant. Recombinant DNA techniques were first used for prenatal selection of sickle cell disease in 1982. However the most common screening used in most countries is based on protein screening because for many diseases it is the lack of functional enzyme that is important, it may not matter what allele you have as long as some protein can be made (see the earlier example of PKU).

For a growing number of known genetic diseases, methods have been developed to detect the genetic defect early in fetal life (For methods of genetic screening see the Chapter on Genetic Technology). These methods rely on removing a sample from the fetal material and analysing it. There are different stages at which fetuses can be screened for genetic disease or abnormalities. As far as the ethics and the distress and the health risk to the mother are concerned, the earlier the better.

Fetal sampling is laborious so that currently only a small proportion of the population, can be screened even if it is considered desirable. Ultrasound is routinely used, and has the advantage of being non-invasive. Different methods may be combined, for instance the first screening may be maternal blood sampling, and if the level of certain proteins (e.g. alpha-fetoprotein) is abnormal, there is greater risk that the fetus may have some problem such as spina bifida or a chromosomal problem, like Down's syndrome. Then further testing is needed to check the result of a blood protein test, as still in most cases with an unusual protein level the fetus is normal.

Samples of placenta or fetal tissue may be taken from those fetuses considered at high risk, i.e. those of older mothers or parents who have a history of genetic disease. The older technique used is amniocentesis, where cells from the amniotic fluid are removed and grown in the laboratory for analysis. No harm is done to the fetus as the fetus is surrounded by discarded cells in the amniotic fluid which are no longer needed for further growth. The fetal samples can be taken at 11-16 weeks. It is now possible using very sensitive genetic probes to take a sample of the chorionic villi (membranes around the fetus) at 6-9 weeks and analyse the fetal DNA directly to determine whether it has a specific genetic defect, with the technique of chorionic villi sampling. Like amniocentesis there is a 1-2% risk of miscarriage after the sampling due to the procedure, which is why they are not general.

We are still unable economically, ethically, or socially, to screen every fetus for so many diseases, with these techniques. Currently efforts and resources are focused on parents with higher risk, however, the latest screening techniques allow hundreds of samples to be tested with over ten thousand different probes simultaneously, which allows low cost routine screening, which could enter widespread use.

In the mid-1990s mail order companies in the UK conducted cystic fibrosis tests. In the future it will be possible to routinely use the technique where the few fetal cells that can be found in the mother's blood are isolated, and analysed. It is already possible to use preimplantation diagnosis to look at an embryo before implanting it in the mother, when IVF is used. However, IVF is not an option for general use in developing countries at present as medical resources are limited. It may be an option for those parents who refuse abortion of a fetus, but have a high risk of passing on a genetic disease.

Q1. Would you be interested to know the genetic profile of your embryo/fetus before birth? Why?

E5.2. Therapy or abortion after prenatal diagnosis?

The general aim of prenatal diagnosis is to reassure mother's who are worried that their fetus has some disease. They may avoid pregnancy without the possibility of such reassurance that the fetus did not inherit some disease, or abort because they worried about some ill effect from a drug used before the mother knew she was pregnant.

Prenatal diagnosis does not always mean an affected fetus will be aborted. In fact, medically it should be separated. There are a number of advantages for the parents who want to bear a child regardless of the fetus's condition. The first is that some therapy may be possible to solve the problem, or even to lessen the seriousness of the condition. There are even cases of surgery being performed on a fetus and the fetus being returned to the mother's womb. Another benefit is knowledge, to be informed before birth and emotionally prepared.

Human procreation is associated with a high degree of error, because when genetic elements rearrange there are often mistakes. The number of fertilised embryos with genetic abnormalities may be about 70%. Most of the genetically abnormal embryos are never implanted, or are spontaneously abort in early pregnancy. But some babies are born and will die later, some have a painful life, while others do not.

Q2. Is it right to terminate a pregnancy if the unborn child has a genetic/medical defect which cannot be treated? Is it right to terminate a pregnancy if the unborn child has a genetic/medical defect which can be treated?

E5.3. Ethical issues of prenatal diagnosis

If a fetus has a serious genetic impairment, with a consequence of serious mental deficiency, some people might say that the fetus does not, and will not in the future, have a "life" as "normal" humans have a life. While the potentiality is different, it is impossible to define what is a normal human life, and it is discriminatory to claim that some human beings do not have a life worth living. One of the achievements of the twentieth century has been to fight for the rights of all persons, and to not allow some people to claim other people are inferior.

There are quality of life issues, but can we deny the potential for spiritual relationship between God and the most diseased forms of human life? Severely retarded individuals may not appear spiritually aware - but can people judge? Many religions would argue there are no "worthless" lives. We should build a society to prevent discrimination, and make life easier for those with disability, whether or not we accept using prenatal screening.

The ethical issues that remain are questions of whether mother’s can choice to follow up diagnostic tests of the embryo or fetus, which can provide useful information for preventative action, with choices for abortion. This controversial issue will remain a divided question in the following centuries the same as it has for millennia in writings about the ethical issues of abortion. Different countries have contrasting approaches to these questions. This book chapter does not take a position on this topic, except an observation that it is a difficult moral dilemma and each culture has different ways to cope with the lack of consensus that is universal on the morality of these questions.

E5.4. Whose choice?

We can take the viewpoint of the child to be, the mother, or the family, and all views are important in cultures which are family-centred. Once we start to take society’s broader view, there are more ethical questions about interference in reproductive rights of persons.

Although we will continue to see ethical division over the morality of prenatal genetic screening, with some people continuing to reject it, ethically we need a system to respect the informed choice of families. They must decide their responsibility to present dependents and future children, and think firstly of the children's quality of life. The correct decision is not to say do not abort or abort, but it may be the decision made by the informed mother. Society may put limits on the extent of this choice, e.g. maybe for sex selection, and maybe for fears of misuse.

Q3. Imagine you are the government minister in a resource-poor country with a large population. What policy options to govern health services related to prenatal diagnosis would you offer?