Having a child who suffers from a major genetic disease can be one of life's most challenging surprises, often demanding a lot of time, money, and emotional strength. But with the introduction of prenatal genetic testing in the 1960s, the element of surprise has been reduced for some childhood genetic diseases. Prenatal genetic tests let expecting parents find out in advance whether their child will be born with a major disability or terminal disease, and, in the case of a positive diagnosis, offer a choice: prepare for the life-altering challenge of raising a child with major health problems or abort the pregnancy.
It’s a choice no would-be parent wants to face. But given the option, many choose abortion. In the case of Down syndrome, one of the most common prenatally diagnosed diseases, a 2012 American study found that nearly 70 percent of women with a positive diagnosis decide to terminate the pregnancy. In the United Kingdom, 90 percent of women choose abortion. And in Denmark, after the introduction of a nationwide prenatal screening program to identify high-risk pregnancies in 2004, the number of children born with Down syndrome was reduced by half as more cases were detected during pregnancy and the women chose to abort. These numbers are revealing: When a prenatal genetic test gives expecting parents a choice, most of them choose not to have a child with a major genetic disease or disability.
In the case of Down syndrome, a 2012 American study found that nearly 70 percent of women with a positive diagnosis decide to terminate the pregnancy.
More expecting parents will soon be faced with this choice, as a new genetic testing technology greatly expands the scope of prenatal testing. This technology, called cell-free fetal DNA testing, doesn’t require the moderately invasive medical procedures of older prenatal tests. In the older tests, like amniocentesis or chorionic villus sampling, fetal DNA is taken from cells in the placenta or the amniotic fluid, using a needle that goes inside the mother's uterus. This poses a small but non-trivial risk to the fetus. Because of this small risk and the invasive procedure required, physicians don't recommend traditional prenatal genetic tests unless there is already a reason to think that the fetus has a higher risk of a genetic abnormality. The newer prenatal tests, however, are based on a much more accessible source of fetal DNA: the mother's bloodstream. That fragments of fetal DNA naturally circulate in the mother's blood is something scientists have known for decades, but, until recently, DNA analysis technology wasn’t good enough to base a test on these fragments.
It turns out that there is enough fetal DNA in the mother's blood to put together a complete genome sequence of a child before it is born, as a pair of studies demonstrated in 2012. That means that any genetic analysis that you can perform on someone after birth can also be performed long before birth—as early as the first trimester. While such an analysis is also possible with DNA obtained through an amniocentesis, the ease and low risk of cell-free fetal DNA testing means that screening for a broad range of genetic conditions could soon become a routine part of every pregnant woman's prenatal care. The societal and ethical implications are tremendous: Routine, broadly targeted prenatal genetic testing means that having a child with a major genetic disease or disability will largely cease to be a surprise and instead become a deliberate choice.
Taken to extremes, that kind of broad eugenic decision-making may sound disturbingly dystopian. We're not quite there yet. Cell-free fetal DNA tests have been available in the clinic since 2011, but they currently target the small set of common genetic diseases covered by traditional tests. The commercial feasibility of more comprehensive analyses is still limited, in part because cell-free fetal DNA testing requires a technical trick to avoid having the result skewed by the fragments of maternal DNA that also circulate in the mother's blood. But the technology is developing rapidly, and non-invasive prenatal genetic testing will soon become much more common. As it does, we need to address the key ethical and social challenge of prenatal genetic testing: When should a pregnancy be terminated for genetic reasons?
Ultimately, that question must be answered individually by the expecting parents who face a positive prenatal diagnosis. But what they decide is strongly influenced by the information they receive. How will their lives be affected by having a disabled or seriously ill child? What kind of life will the child have?
To answer these questions, expecting parents need to make sense of an overwhelming number of complicated medical details that are difficult to navigate without competent genetic counseling. Many diseases detected by prenatal tests—Down syndrome or sex chromosome trisomies like triple X—don't always have severe symptoms. Other diseases, like Huntington's, are invariably fatal, but symptoms don't develop until middle age. Some, such as hemophilia, are not curable, but are fully treatable, allowing patients to live relatively normal lives. And these might be the easy cases. In the future, tests could cover diseases that we can’t predict with complete accuracy—what should a pregnant woman decide when told her child has a 60-percent chance of developing autism, or an 80-percent chance of having a pediatric cancer? To make such difficult decisions in a way they won’t regret, expecting parents need good genetic counseling.
In the future, tests could cover diseases that we can’t predict with complete accuracy—what should a pregnant woman decide when told her child has a 60-percent chance of developing autism?
Unfortunately, competent genetic counseling is in short supply. We lack the infrastructure to get expecting parents the information they need: Physicians generally aren't trained to help their patients interpret genetic test results, and there aren't enough professional genetic counselors to meet the growing demand. As a team of bioethicists, led by Duke University researcher Subhashini Chandrasekharan, wrote in a recent review of these new tests, "given the speed with which [non-invasive prenatal testing] has entered clinical practice worldwide, has moved into lower-risk populations, and has expanded to detect additional conditions, conveying reliable and accurate information to all patients in a timely manner is virtually impossible."
And then there is the question of what role the government should play. Because abortion is one of the most radioactive issues in American politics, it's hard to imagine that any kind of intervention by legislatures and executives would be a carefully considered effort to help expecting parents make better decisions. The Ohio legislature might take the decision out of the hands of parents altogether—it is currently considering a bill to ban abortions for Down syndrome. Other states don’t go quite that far, but have passed laws mandating what information needs to be given to parents who receive a prenatal diagnosis. In 2014, Pennsylvania enacted a law requiring that a prenatal Down syndrome diagnosis be accompanied by "up-to-date, evidence-based information" that explains the physical and social development of affected children, their life expectancy, and contact information for national and local Down syndrome advocacy organizations.
Writing in a recent issue of PLoS Biology, New York University bioethicist Arthur Caplan argues laws like Pennsylvania's are "deliberately positive about Down syndrome" and "seek to spin the message given by doctors and counselors about Down syndrome in a particular direction"—away from abortion. By doing this, such laws "overturn the long-standing foundational ethical norm of genetic testing and counseling—neutrality in the provision of information," and instead promote "a more disability-friendly normative message." But less partisan sources of information aren't necessarily unbiased either—Chandrasekharan and her colleagues note that medical textbooks and the peer-reviewed literature "often focus on the clinical symptoms, or negative aspects of a genetic condition."
Perfectly balanced or neutral information about a genetic disease is an unrealizable fantasy anyway—how parents and children experience the disease is subjective, and doesn’t only depend on the medical facts. The factors that lead expecting parents to abort or continue a pregnancy after a prenatal diagnosis are just as personal. Prenatal diagnoses are like many other recent developments in genetic testing—developing the technology is the easy part. The real challenge is helping people use genetic information to make the best decisions they can.
Inside the Lab explores the promise and hype of genetics research and advancements in medicine.