The following article appears in the March/April 2007 issue of Technology Review.

A 38-year-old woman with fer­tility problems has three sons but wants a daughter to round out the family. She uses in vitro fertilization (IVF) to conceive and asks her doctors to transfer only female embryos; the male embryos are destroyed. Is this use of reproductive technology acceptable? What if a couple with a family history of diabetes wants to use IVF to select an embryo without a ­particular gene linked to diabetes risk? If afflicted family members largely have the disease under control, are the prospective parents justified in choosing in vitro fertilization so that they can bear a child with a lower chance of developing it at all?

Such questions are becoming more common as preimplantation genetic diagnosis (PGD)–testing performed after an egg is fertilized in vitro but before the resulting embryo is transferred to the womb–makes it possible for some prospective parents to select specific embryos before a pregnancy begins. Originally developed more than a decade ago to identify the rela­tively small number of embryos at high risk for serious or fatal genetic diseases, such as Tay-Sachs, the technology now encompasses genetic tests for a growing number of illnesses, including some that are not necessarily fatal. And these tests are available to more and more parents as the popularity of in vitro fertilization skyrockets; approximately 50,000 babies are born through IVF in the United States every year.

All this heightens the ethical concerns that have plagued PGD from the start. As more genes associated with the likelihood of disease are uncovered, the possibility of a truly preventive medicine is within the grasp of many parents. But with that possibility come risks. How well will any one test deliver on its promise of a healthy child? Will parents feel obligated to use genetic testing without adequately understanding its benefits? What kinds of genetic tests will parents want? Recent findings suggest that an increasing number of parents using IVF are choosing embryos according to sex, and it’s possible to imagine them one day choosing embryos based on other nonmedical traits, such as hair color, height, or IQ.

Preimplantation genetic testing is available only to those who opt for IVF–which now generally means people with fertility problems or a family history of a fatal genetic illness. Though IVF is gaining in popularity, it remains an expensive and often difficult procedure. But the grounds for choosing it are changing: some people, for example, are now using it to select embryos without genes linked to particular cancers–even if the correlation is fairly weak. If parents increasingly choose IVF because it will offer them the opportunity to tailor their children’s genetic traits, will the economic division of society become even deeper–separating those who can afford IVF (clinics in the United States generally charge between $6,000 and $16,000) from those who cannot?

“This is a potentially disruptive technology, one that can change the social structure and order,” says David Adamson, president-elect of the American Society for Reproductive Medicine and director of a private fertility clinic in northern California. “It will move us toward a preventive approach to medicine and could change our approach to reproduction.”

Tests are already available for genetic variants associated with a thousand conditions, including deadly childhood illnesses and adult-onset cancers, and more genes associated with disease risk are being discovered every day. Any such gene could be a target of PGD. Santiago Munné, director of Reprogenetics, a genetics laboratory headquartered in Livingston, NJ, says his lab has tested embryos for more than 150 diseases or risk genes–most recently for a gene variant known as BRCA1, which raises the risk of breast cancer.

Little data yet exists on the use of preimplantation genetic tests. But late last year, the Genetics and Public ­Policy Center at Johns Hopkins University released a report in the journal Fertility and Sterility presenting some of the first statistics on the use of PGD nationwide. “We wanted to get a sense of how much PGD was being done, and why,” says Susannah Baruch, the center’s director of reproductive genetics and lead author of the report. “Without solid data, it’s difficult to analyze outcomes for PGD babies or to help prospective parents make decisions about whether to pursue PGD.”

The researchers surveyed all the fertility clinics in the United States that offer IVF, asking questions about the types of preimplantation tests they administer, how they make ethical decisions, and how they think testing should be regulated. About half of those clinics responded. According to the survey, screening for chromosomal abnormalities that can lead to implantation failure or miscarriage, or for disorders linked to chromosome duplication or deletion (such as Down’s syndrome), represents two-thirds of all PGD testing. Tests for genetic diseases such as cystic fibrosis account for another 12 percent. Forty-three percent of clinics said they had received requests for PGD that they felt raised ethical questions; most of these were from parents who wanted to select the sex of a child for nonmedical reasons. The survey found that this use of PGD is fairly common: almost one in ten tests was for nonmedical sex selection, a service offered by 42 percent of clinics.

Since it is the only PGD test that is often administered without medical justification, sex selection is especially contentious; some fertility clinics will not offer it, and some ethicists say that ­nonmedical sex selection opens the door to other types of nonmedical testing. But other people argue that biological enhancement through genetic screening is not so alarming, or at least not so different from other types of advantages that are already enjoyed by a certain privileged sector of the population. “I don’t think testing for freckles or blond hair or musical aptitude is a morally bad thing to do,” says Arthur Caplan, director of the Center for Bioethics at the University of Pennsylvania. “I think parents will want to do it, so I think this will expand rapidly.”

Testing for medical purposes brings its own set of problems. Only a limited number of genetic variations present the kind of clear-cut case for which PGD was originally developed: the certainty of a serious or fatal disease. But what about testing for genes that merely raise the risk of a disease? Or for genes linked to a relatively manageable disease, such as diabetes? How serious must a disease be to justify the costly and potentially risky process of IVF?

“That is a major debate in the profession,” says George Annas, chair of the department of health law, bioethics, and human rights at the Boston University School of Public Health. Another problem is that parents may eventually find themselves with more information than they or their doctors know how to use. As more disease-linked gene variants are discovered–and the list is rapidly growing–parents will face so many choices that it will be difficult, if not impossible, to determine which genetic combination will produce the healthi­est child.

In the United Kingdom, a government body licenses fertility labs and regulates which tests can be administered. But the United States has fewer rules; it is one of the few countries, for example, that permit nonmedical sex selection. “Today, in this country, the clinics are the gatekeepers,” says ­Vardit Ravitsky, a bioethicist at the University of Pennsylvania. “If you have cash and can find a clinic to provide the service, you can get it, whether it’s a test for Huntington’s disease or sex selection.”

So decisions regarding PGD are left in the hands of doctors or clinics. Professional societies provide some ethical guidelines–the American Society for Reproductive Medicine, for example, recommends against sex selection for non­medical reasons, though it has little to say about other aspects of PGD. But voluntary guidelines regulating a profit-driven industry may not be enough to help prospective parents. “I think there will be people hyping the advantages of this, which will be just like pharmaceutical advertising today,” says Caplan. “I think people will be guilted into doing this, rather than choosing it.” They may also be “guilted” into testing that doesn’t make good on the promise of a healthier child; most of the newly discovered genes have relatively weak correlations with disease or play small roles in complicated processes, and some may affect the body in ways that scientists don’t yet fully understand.

Some kind of regulation for preimplantation genetic testing is needed, but the rules must focus not on limiting which tests a parent can choose but on making sure that clinics can scientifically justify the claims made for each test. Then parents and their doctors can begin to make informed choices. “I definitely think the government has a role to play in regulating the safety and quality of tests and in the application of tests,” says Adamson. “But the final choice, once tests are considered to be scientifically legitimate, should be left up to patients and physicians.”