In 1996, Monique and Scott Collins were among the first couples in North America to choose the gender of their child. It’s called family balancing and they took advantage of medical technologies that, to some, represent a great stride forward in family planning. In an interview some years later, Monique said “After having two boys I thought they needed a sister.”
To some, genetic testing signalled the beginning of a slippery ethical slope. The assumption was that, while choice was currently limited to gender, it wouldn’t be long until parents could determine other attributes ranging from eye colour, to being good at math, to perhaps anything and everything in between. Minds are free to wander, and certainly many did, often well beyond the bounds of the medical community.
Henry Louis Gates Jr. says, “We are living through an era of the ascendance of biology, and we have to be very careful about reproductive technology. We will all be walking a fine line between using biology and allowing it to be abused.”
Science can offer many things today that in the past were little more than fiction or wishful thinking. Today we can test our genes for more than 1,500 diseases – a number that is expected to double in the next decade. Some tests are of interest to prospective parents, giving them the opportunity to, as with the Collins family, choose the gender of their child, but also to ensure that some hereditary conditions aren’t expressed, such as cystic fibrosis and muscular distrophy. That’s the short version. The longer version is, well, not so simple.
First things first
While some genetic tests may be new, there are many others that have actually been with us for quite a while and are considered to be a routine aspect of prenatal health. Andrea Jensen, a mother of four in Burlington, Ontario, is perhaps more familiar with these tests than most. At the outset of her fourth pregnancy, she had undergone two genetic screens – her age-related risk and her blood work – and both indicated a risk for Down Syndrome. She says, “My age-related risk was high – I was 37 – for having a Down’s baby. When I had the first and second blood screens done, my results were one in 50 that my baby could be born with Down’s.”
During her ultrasound at 13 weeks, she underwent a third screen. “That was when they noticed that the nuchal translucency was higher than average.” A nuchal translucency test measures the fluid under the skin at the back of the neck of the fetus; fetuses with Down Syndrome tend to have a larger amount of fluid, indicating an increased risk. Coupled with the other screens, the nuchal translucency test put Andrea within the 90th percentile for risk of Down Syndrome.
She says, “I tried just to keep my emotions out of it, even while realizing the full impact of what that news did or didn’t mean. All the doctors will say is that you have a positive nuchal translucency. I asked for the number and it was on the high end of normal. The fact that it wasn’t a huge number – such as one that infers a one in two chance or something – made me feel a bit better. It was high, but it was within the range of normal.”
For Andrea, the next step was a diagnostic test, which represents, in a sense, the second tier of genetic testing. There are two done in Canada, chorionic villous sampling, which samples tissue from the placenta, and amniocentesis, which samples the fluid surrounding the fetus.
Andrea and her doctor opted for an amniocentesis though, given the two-week waiting period for a result, life certainly didn’t get any easier.
She recalls, “For some reason my paperwork got lost in the shuffle, and the two weeks came and went and I’m thinking that I can handle two weeks, but I can’t handle longer than two weeks.” She called to see what was up and found that the results of the amniocentesis were negative.
But, while they may form the basis of what we think of as genetic testing, certainly no one is writing potboilers about amniocentsis. Those tests are useful in gauging risk and, for Andrea and her husband Pete, they brought a welcome piece of mind. It’s a lot, but those tests can’t do much more than that. Molecular testing, however, is another matter entirely.
Dr. Chumei Li, the director of the Clinical Genetics Program McMaster University Medical Centre says, “This is where most of the new breakthroughs are happening these days. What we do is help patients identify a genetic cause for their problems through an analysis of DNA, at times even prior to pregnancy, so that the family can make reproductive decisions. If there is a family history, and they are found to be carriers, then prenatal diagnosis can be done.
“If a condition runs in the family and parents want to have an unaffected child they can go to in vitro fertilization. After the fertilization of the egg, we culture the egg until it becomes a tiny little embryo. With the technology we have now, we can extract one or two cells and test them to see if there are mutations.”
This information then informs the decision of which embryo will be chosen for implantation, with the choice going to those that are free of the troubling genes.
In Canada, preimplantation (generally known as PDG) is attempted only when there is a known lethal condition that runs in a family.
Susan Zeesman, a geneticist at the Hamilton Health Sciences Centre says, “PGD can be a wonderful thing for families at risk for genetic disease but it is very expensive, not always successful and can be a bit of a roller coaster ride.”
Molecular testing isn’t something that couples would engage in lightly, and even then, it is only available when the parents are known to be carriers of a specific gene.
As for designer babies, “we aren’t even close to anything like that yet,” says Dr. Li. “At most, in about eight to 10 years, we may be able to sequence the human genome for our patients. How to make sense of this, however, will actually be the bigger problem.”
Genetic tests for you and me
Still, that’s far from the end of the story as far as genetic testing is concerned. Prenatal tests can command a lot of press, but some of the most impressive advances these days aren’t in reproductive or prenatal medicine, but further along in the life course. Simply put, genetic testing in adults and children has the power to revolutionize how you view your family’s ongoing heath care.
Here's how. Let’s imagine that, while you are perfectly healthy and have been all your life, you were to learn that you are predisposed to some forms of cancer, Alzheimer’s, or have a highly elevated risk of alcoholism. What if you knew that you carried a genetic marker for diabetes, or have a remarkably enhanced risk of thrombosis? No doubt, you and your doctor might find this information immensely helpful. You could take steps now in order to lessen risk later on, ranging from lifestyle choices, to choosing medicines, to taking steps to lessen harmful side effects of surgery.
Not so very long from now, this may be precisely the kind of information everyone will have about themselves, and more. Genes have been isolated for many illnesses and, while having them doesn’t mean you will get them, having that knowledge can help ensure that you don’t get them. In light of the promise of this kind of testing, it has been said that, “There is no such thing as a healthy person.” Our genes, it is believed, can grant us what would amount to a complete diagnosis, even before we run into any specific health issues.
While family balancing may get all the headlines, there are other areas
of genetic testing that, ultimately, will get the final word.
How far can you go?
is the question that looms in the minds of many whenever discussion of
genetics is raised. Movies and novels, such as Michael Crichton’s novel
Next, in which genes are held responsible for a vast range of troubling
things, certainly blur the boundaries between fact and fiction.
and centre is the fear of babies genetically ‘designed’ to reflect the
wishes and the whims of parents. Dr. David King, founder of the UK Human
Genetics Alert, leads the call. Left unchecked, he fears that, “Parents
will be allowed complete carte blanche to choose the minutest
characteristics of their children, which I think will be disastrous for
Disastrous, yes, but is it really possible? “The
technology to do it perhaps exists, at least in theory,” says Dr. George
Carson, director of Maternal Fetal Medicine at Regina’s Qu’Appelle
Health Region, “but we have a variety of ethical guidelines that are
strictly adhered to that limit the applicability of this technology
should it become viable.”
In the case of genetic testing,
including gene molecular testing and gene therapy, Dr. Carson notes that
“it is known that the individuals involved either have the disease or
are carriers, and the gene has been properly characterized.” Without
this, searching for specific genes is, at best, like looking for a very
small needle – and most likely one that you may not recognize even when
you see it – within a very large haystack. Dr. Carson says, “That isn’t a
technological feasibility” and isn’t likely to become feasible anytime
Originally published in ParentsCanada magazine, Summer 2009.