IntroductionNew developments in testing in pregnancy for genetic conditions
A team of scientists in the US have just reported identifying a whole fetal genome from a sample of the mother’s blood and a sample of the father’s saliva, taken at the 18th week of pregnancy. Dr Susan Kelly considers the implications:
This is the latest report in the fast-moving international development of so-called non-invasive prenatal genetic diagnosis, tests that can be performed early in pregnancy and without the risks of miscarriage associated with current invasive tests (roughly 1 in 100). It follows similar reports of experimental non-invasive prediction of the whole fetal genome from a sample of blood from a pregnant woman by two other groups.
Non-invasive prenatal diagnosis of Down Syndrome and other conditions caused by extra chromosomes (known as trisomy) in the fetal DNA, are also being developed rapidly. Most recently, a group reported 100% accuracy with such a test, with the ability to provide pregnant women with an individualised ‘risk score’ for trisomy.
That the most recent US finding on the whole fetal genome is being widely reported in the UK media accompanied by a fetal ultrasound photograph underlines our familiarity with existing forms of fetal screening. While currently prohibitively expensive and of unknown accuracy, non-invasive whole fetal genome testing raises the possibility of testing a fetus for thousands of genetic conditions at once, early and safely. With the costs of sequencing dropping rapidly, and lots of commercial interest, the possibility of whole fetal genome screening looms in the future. This prospect raises a host of ethical and societal issues, as well as a range of important clinical concerns – who will counsel prospective parents about the meaning of thousands of genetic conditions, how will prospective parents determine what they do or do not want to know, how accurate will the tests be, and how complex will reproductive decision-making become when this genetic information is combined with information about the health of a fetus gained through other forms of testing, such as traditional ultrasound? Who should decide?
Fetal genetic material in accessible form was identified in the blood of pregnant women in 1997. Since then, in the UK and other parts of Europe, tests have been developed for non-invasive prenatal genetic testing for a limited number of conditions: a few single gene conditions; fetal blood type, important in cases where the mother and the fetus are at risk of having incompatible blood types; and for fetal sex, important in cases where a fetus is at risk of a serious disease linked to the X chromosome. In the United States and parts of Asia, non-invasive prenatal blood tests for Down Syndrome are on the market and several companies are in heated patent litigation over these products. (Non-invasive prenatal blood tests for Down Syndrome are in development in the UK and Europe but are not clinically available.) The new tests suggest that prenatal testing might be more easily directed toward conditions a fetus is at risk of inheriting (such as cystic fibrosis or beta thalassemia), as well as for genetic mutations that are not inherited but occur ‘de novo’ (Down Syndrome is usually such an occurrence, as are a range of other, more rare conditions). That non-invasive genetic tests are seen to be the future of reproductive testing is attested to by the large number of presentations at the upcoming meeting of the International Society for Prenatal Diagnosis devoted to the topic. What might this future look like?
We and other researchers have been studying aspects of this future by studying relevant public attitudes, the preferences of pregnant women, and the views of health care professionals. In the UK, it has been found that the public is generally accepting of the medical benefits of non-invasive testing, but prefer to see the tests administered by a physician, in part in order to provide sufficient counselling (people should know what they are testing for). Pregnant women have been found to be generally happy about the benefits of non-invasive testing, and to appreciate having decisions following testing being made earlier in pregnancy than with conventional tests. In the media, questions are regularly raised about increased numbers of abortions following earlier and easier prenatal genetic testing, while proponents point to rights to information and the ability to prepare for the birth and care of an affected child.
This research has been conducted in the context of limited testing, not the whole genome approach that appears to be on the horizon. It is not known how prospective parents will negotiate this wider form of ‘choice’. How many people will choose to access testing in the private, commercial sphere, if such tests are not made available through health systems, and how much will they be willing to pay? Who will provide counselling to such patients? How – or will – states step in to regulate? Will such testing become embroiled in debates – and policy - about abortion? Will fetal testing become even more routine, and will ideas of what is ‘normal’ and acceptable in a fetus come under even more scrutiny? Diagnosis of a wide range of conditions is currently available for embryos created in fertility clinics in the UK. Although this is not available routinely and doesn’t involve aborting a fetus, questions of choice are already before us.