Noninvasive Whole-Genome Sequencing of a Human Fetus

On June 6, 2011 Science Translational Medicine published “Noninvasive Whole-Genome Sequencing of a Human Fetus” by Jay Shendure, et al. In part the abstract states:

“Analysis of cell-free fetal DNA in maternal plasma holds promise for the development of noninvasive prenatal genetic diagnostics. Previous studies have been restricted to detection of fetal trisomies, to specific paternally inherited mutations, or to genotyping common polymorphisms using material obtained invasively, for example, through chorionic villus sampling. Here, we combine genome sequencing of two parents, genome-wide maternal haplotyping, and deep sequencing of maternal plasma DNA to noninvasively determine the genome sequence of a human fetus at 18.5 weeks of gestation…with 98.1% accuracy…Although technical and analytical challenges remain, we anticipate that noninvasive analysis of inherited variation and de novo mutations in fetal genomes will facilitate prenatal diagnosis of both recessive and dominant Mendelian disorders.”

Prior studies were restricted to detection of fetal trisomies (21, 18, and 13) but as the authors state, it is now anticipated that this type of testing will “facilitate prenatal diagnosis of both recessive and dominant Mendelian disorders.” Medical ethicist Harriet Washington, Ph.D., fears parents could use genome sequencing to predict and selectively abort children that don’t meet certain standards – not just for diseases, but for things like hair and eye color. Of note, Dr. Washington is a frequent commentator on ethics who seems to show up in the popular press on a regular basis. She was just quoted in one of the articles about Mayor Bloomberg and a proposed ban on large sugary drinks in NYC. I’m not saying that she is without qualifications or that she doesn’t bring up a valid point, but I’m a little leery of people who make a living out of commentary. I think that if we’re going to have a valid debate about ethical issues we need to speak from facts and not inflammatory rhetoric. And the traits she mentions, hair and eye color are not conclusively known to be Mendelian (they are thought to possibly involve more than one gene). It is doubtful that this testing could be used to make these determinations.

What does the Church say about prenatal testing?

Directive #50 of the Ethical and Religious Directives for Catholic Health Care (ERDs) states that prenatal diagnosis is permitted if it does not threaten the life or physical integrity of the unborn child or mother or subject them to disproportionate risk; when the diagnosis can provide information to guide preventative care for the mother or pre- or postnatal care for the child; and when the parents, or at least the mother, give free and informed consent. Prenatal diagnosis is not permitted when undertaken with the intention of aborting an unborn child with a serious defect.

So, in actuality, from a Catholic standpoint, this type of testing, using serum from the mother and saliva from the father, would be ethical and preferred to either amniocentesis or chorionic villus sampling. And with a 98.1% accuracy rate we could be more confident in the results (less false positives means less emotional distress associated with the false positives). The challenge comes with deciding if we should try to determine the motives of the parents requesting the testing, working to have in place adequate counseling for parents, and providing proper support (financial, social, and pastoral) for parents who ultimately choose this testing in a Catholic health care setting.

I’ll leave the discussion about the exclusion of the poor and middle-class from the use of this expensive new technology to another post.

What do you think about this new type of testing? Do you believe Catholic hospitals or the Church has an obligation to determine parental motives? Does secular society?

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