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Get ready for the flood of fetal gene screening

Posted Feb 18 2011 1:53pm

In a recent article in Nature, Henry T. Greely, proposes that the time when prenatal genetic screening may be commonplace is closer than, well, I thought.

The world’s news media was buzzing last week after researchers showed that a blood test for mothers could detect Down’s syndrome in their fetuses[1]. Last month, two research groups independently published proof that the fetal genotype — the genetic status at a given locus — can be derived for thousands of sites from samples of fetal DNA with just a 10-millilitre blood draw from a pregnant woman[2, 3].

[1] Chiu, R. W. K. et al. Br. Med. J. doi: 10.1136/bmj.c7401 (2011).

[2] Lo, Y. M. D. et al. Sci. Transl. Med. 2, 61ra91 (2010).

[3] Fan, H. C. & Quake, S. R. Nature Precedings doi:10.1038/npre.2010.5373.1 (2010).

Until now, the main prenatal testing has been for Down Syndrome. It is not common:

Prenatal genetic testing has been clinically available since the late 1960s, but the costs, inconvenience and especially the miscarriage risks have limited its use. Each year, less than 2% of pregnant women in the United States undergo amniocentesis (in which a small amount of amniotic fluid containing fetal cells is taken for analysis) or chorionic villus sampling (CVS — in which fetal tissue is extracted from the placenta). Both procedures increase the risk of miscarriage. Until now, any given sample could be tested for only one or two conditions, typically chromosomal abnormalities such as trisomy 21, the cause of Down’s syndrome.

It is uncommon, but it is offered in high risk situations (older mothers). Since the test has been offered, the prevalence of Down Syndrome has dropped significantly. This in spite of the fact that older mothers are more common now.

Amniocentesis is obviously invasive, resulting in risk to the unborn child. But a blood draw would be a non-invasive prenatal genetic diagnosis (NIPD).

The potential of NIPD goes way beyond Rhesus screening. Two of the leading researchers in cell-free fetal DNA testing — Dennis Lo of the University of Hong Kong and Steve Quake of Stanford University in California — use different methods to analyse fetal cell-free DNA from maternal serum. Each has demonstrated the ability to detect aneuploidies — missing or extra chromosomes, such as in trisomy 21 (refs 5, 6). Last month, both researchers published proof that the fetal genotype could be derived for thousands of sites from cell-free fetal DNA2, 3 — demonstrating the possibility of using maternal blood to test for all fetal genetic traits.

The methods demonstrated are already interesting commercial firms:

Commercial firms are already interested. Sequenom in San Diego, California, is working with Lo; another, Artemis Health of Menlo Park, California, is working with Quake; and still others are also exploring the technology. For-profit development of these methods seems likely within five years, at least for chromosomal abnormalities, such as trisomy 21, and possibly for single-gene traits.

My insurance plan will pay for prenatal genetic testing, but not for genetic testing of a child. I find that thought a bit chilling.

Until now, prenatal genetic testing has been relatively uncommon. The ethics discussions have been largely academic. Important, but academic. The time for academic discussions of the ethics is drawing to a close.

Professional organizations, in medicine and in genetics, need to get involved, both in training their members about these technologies and in beginning to consider guidelines for their use, especially with regard to informed consent. Regulators, companies and consumer advocates need to be talking about pathways for assuring the safety, efficacy and quality of NIPD testing. In the United States, the Food and Drug Administration should start that process immediately. And it is time for ethics commissions, such as the US Presidential Commission for the Study of Bioethical Issues, to report on these issues.

Most importantly, we need to start conversations, between all those concerned, about the limits, if any, to place on this powerful technology. Whether we view NIPD gladly as a way to reduce human suffering, warily as a step towards a eugenic dystopia, or as a mix of both, we should agree that the better we prepare, the more likely we are to avoid the worst misuses of this potentially transformative technology.

What disabilities will eventually have genetic screening possible? How will we as a society take on the ethical challenges? If the drop in Down Syndrome is any indication, I think there is reason to take this discussion very seriously. Now.

  1. Tweets that mention Autism Blog - Get ready for the flood of fetal gene screening « Left Brain/Right Brain --
    [...] This post was mentioned on Twitter by Kev, Wolf Cocklin, D., Robbo, meredith hart and others. meredith hart said: RT @Dianne_: Fetal gene screening becoming commercially available. Time to discuss the ethical implications #LBRB [...]
  2. passionlessDrone:
    Hi Sullivan - Fascinating. IIRC, I ran into something similar on the Interwebs a while ago about the foundation for this, something about the ability to occassionally find a y chromosome in the blood of a woman who had given birth previously as a result of backflow from the fetus. Very neat stuff! That being said, there are already people doing something similar; testing for maternal antibodies associated with autism in the mother. There's a group in California doing it, likely associated with the MIND guys; considering that to my knowledge they haven't yet released what the antibody looks like in their papers. The literature on it is very specific that pregnant women cannot perform the test. Among the many problems that occur to me is that the test is probably not all that precise, certainly nothing like finding trisomy 21. Thanks for posting this, I likely wouldn't have run into it otherwise. - pD

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