A recent USA Today article reported that doctors can now test for 450 genetic diseases. This means that a couple can find out if one or both are carriers of a defective gene that will effect their offspring. Through prenatal diagnosis, a pregnant woman or her preborn child may be tested to see if the child is subject to a genetic defect.

The methods of genetic testing have become safer and more accurate, and can now detect a wider variety of genetic problems before a specific disease actually occurs. For instance, a genetic change, or mutation, that has been found to double the risk of colon cancer for some persons was recently discovered. The research shows that this mutation effects 6% of Ashkenazi Jews. Anyone in this population group can have periodic tests that would detect the early warning signs, allow for treatment, and thereby reduce the risk of colon cancer to near zero. In this case, genetic information allows people to identify and avoid disease.

Thanks to the Human Genome Project, a government-funded effort, the entire genetic mosaic of the human being will soon be known. That will not only enable doctors to develop diagnostic tests to determine if disease is present, but ultimately, in some cases, to intervene and change a person's genetic makeup.

It's important to distinguish genetic screening from genetic testing. In screening, entire population groups are given a test for any evidence of a genetic defect or weakness. Widespread screening can help protect everyone, or it can lead to the knowledge that only specific segments of the overall population are effected or are at higher risk, like the Ashkenazi Jews or African-Americans with sickle-cell anemia.

There are also specific prenatal tests that can ascertain whether an unborn child is effected by some genetic defect or disease. These tests have become more sophisticated, safer, and more accurate. Unfortunately, for many people the immediate response to a positive test result is to end the pregnancy. For others, knowledge is a foundation for hope. In fact, medical research has now come up with ways to correct some defects even during pregnancy, or at least minimize the danger. There are even surgical techniques that can be used to save the life of the unborn child.

As we acquire new knowledge and new testing techniques are discovered, there is also a new array of dangers and problems. Will employers be able to obtain the genetic profile of workers or those seeking employment, potentially using the information to discriminate against them? Will insurance companies and health care plans procure the information and exclude people from coverage? Will the modern-day eugenicist decide to clean up the gene pool by abortion or sterilization? These are questions raised by ethicists and they are communicated to all of us by the media.

The National Conference of Catholic Bishops' (NCCB) Committee on Science and Human Values has produced two very informative pamphlets—one on screening and one on testing. Both draw heavily on the 1987 Vatican instruction Donum Vitae (The Gift of Life), on respect for human life in its origin and the dignity of procreation and on statements of Pope John Paul II.

Because prenatal testing can lead, and often has led, to abortion, Donum Vitae addresses the question: Is prenatal diagnosis morally licit? The response is that if prenatal testing respects the life and integrity of the human embryo and fetus and is directed toward safeguarding or healing the unborn, then all else being equal, the testing is morally acceptable. Pope John Paul II was even more explicit in his 1995 encyclical, Evangelium Vitae (The Gospel of Life), where he says that such tests are morally acceptable when they do not involve disproportionate risks for the unborn child or the mother, and are intended to make early intervention possible or to enable the parents to prepare for and learn how to care for their child.

The principles that apply to prenatal diagnosis can be applied to other types of testing as well. Essentially, if the test is used to provide necessary information for the person or to safeguard others, and it does not lead to euthanasia, discrimination, or denial of treatment, it is usually morally acceptable. But because of rapid scientific discoveries on human genes, we must be prepared for critical analysis.

It boils down to the fact that scientists are not prepared to provide all the ethical reflection or moral guidance we need on these issues. Priests and others in the health care apostolate must deepen their knowledge and understanding, not only of the techniques, but more importantly of the principles. The NCCB pamphlets Critical Decisions and Promise and Peril of Genetic Screening are helpful. With the enormous amount of information coming from the scientists and the media, it's important for all Catholics to read, study, and be ethically informed.

Bishop James McHugh, ordinary of Camden, N.J., is a member of the NCCB Committee for Pro-Life Activities.