Prenatal Genetic Testing: Do You Really Want to Know Your Baby's Future?
PRODUCERS: Kathy McAnally
Listen to the Program
Download MP3 (PC: right-click; Mac: option-click)
New & Noteworthy, 2007
by Jennifer Jongsma
Prenatal tests can provide valuable information about the health of a fetus; they can also raise tough ethical, social, and legal questions.
Since The DNA Files first visited the science and social implications of prenatal testing in Prenatal Genetic Testing: Do You Really Want to Know Your Baby's Future? (1998), scientists have developed few new technologies in this area. Instead they have fine-tuned many of the tests in use, making them less invasive and more accurate. Previously, scans for Down syndrome were performed during the second trimester. Now a nuchal scan, a new noninvasive ultrasound, can check for abnormalities in the first trimester by measuring the swelling on the back of the fetus' neck.
Ultrasound and genetic screening of maternal blood samples remain the most common prenatal tests. These latter tests sample some fetal cells mixed with maternal cells and can only determine increased risk for a genetic disease. Amniocentesis and chorionic villus sampling, although much more invasive because they sample fetal tissue directly, can diagnose certain fetal problems with high accuracy. Neither screening nor diagnostic tests can predict the severity of a disorder, however. Symptoms of cystic fibrosis, for example, range from mild bronchial abnormalities to severe lung, pancreatic, and intestinal difficulties. Parents must decide whether to continue or terminate a pregnancy when the diagnosis is known but the prognosis is undetermined.
Another factor that raises important issues for prenatal testing is the mother's age. Until recently only pregnant women aged 35 and older were routinely tested to see if their fetuses had the extra chromosome that causes Down syndrome. This is the most common chromosomal abnormality among newborns and causes mild to severe learning disabilities as well as other problems such as heart defects. In January 2007, the American College of Obstetricians and Gynecologists (ACOG) recommended that all pregnant women, regardless of their age, should have access to prenatal screening for Down syndrome. While the risk of Down syndrome increases greatly with a mother's age, it can occur in any pregnancy.
When prenatal genetic testing reveals a disorder or deformity, parents often choose to abort. However, parents can avoid such a decision by using preimplantation genetic diagnosis (PGD). PGD allows couples that are using artificial insemination to identify genetic diseases such as cystic fibrosis and hemophilia A before implantation, rather than several months into a pregnancy. This is especially useful when one or both parents know they carry a genetic variation associated with a disorder. More recently, parents have begun using PGD to look for signs of late-onset diseases and cancer susceptibility. For example, certain mutations in the BRCA1 gene confer high risk for breast cancer. PDG can be used to select embryos that do not have the worrisome mutations.
PDG also has the potential to screen for genetic qualities not related to a disorder. For example, parents of a terminally ill child for whom no donor can be found can screen for an embryo that is more likely to be a matched donor. Many ethicists, doctors and geneticists are asking whether these are appropriate choices to offer parents.
Many of the applications of PDG in use would not generally be considered acceptable if made via a prenatal diagnosis or screen. For example, parents can screen for sex in PDG, but many view terminating a pregnancy for that reason as unethical. Many people consider this technology as dangerously close to eugenics, thus scientists, ethicists, religious leaders, and parents are debating where to draw the line.
Original Program Description, 1998
Today, there are a variety of prenatal screening tools that prospective parents can use to look into their baby's future. With procedures from simple blood tests and non-invasive sonograms to more aggressive amniocentesis and CVS (chorionic villus sampling) tests, doctors can now predict some of our most serious hereditary diseases. Yet even if you performed every prenatal test available — a prohibitively expensive undertaking - only about 350 of the more than 4,000 known genetic disorders could be detected. Should medical science promote the availability of these tests?
This program offers a history and description of prenatal genetic testing techniques, which — in the early years of their existence — doctors increasingly felt compelled to prescribe in order to avoid possible malpractice litigation. This program explores beyond the issues of technology, law, and public policy to the thoughts and feelings of women who have faced tough new decisions: First, whether to participate in genetic testing at all. And second, how to respond to the sometimes devastating results. In this show, we'll hear from two women who underwent prenatal tests and received very different results — and learn how they decided what to do about it.
We'll look at how genetic testing affects us in specific social contexts, talking to mothers in an orthodox Jewish community about a Tay Sachs screening and to low-income women in the rural South, where the vast majority of women refuse to get prenatal testing. Then we'll return to the global view with a history of the eugenics movement. You'll hear some opponents voice their fears that today's prenatal testing could result in screening for traits other than diseases. After all, what is "normal"? And we'll be introduced to the issue of short-statured parents seeking to have children who also have achondroplasia, or dwarfism.
As you listen to the program, expect provocative questions about the direction in which reproductive technologies may take us as they are refined and improved. Ethical dilemmas abound, and only an informed public — and informed public officials — will be able to make wise decisions.