Embryo testing zeroes in on genetic diseases

A boon to parents who don’t want to pass on serious diseases, a test that spots gene abnormalities in fertilized eggs draws fire elsewhere

    1 of 1 2 of 1

      Chris Kirby was just 18 when he was riding his bike to work one day and went into cardiac arrest. A bystander gave the Vancouver native cardiopulmonary resuscitation for almost 40 minutes, saving his life. Now 34, Kirby is on the waiting list for a heart transplant because of his hypertrophic cardiomyopathy. Although the disease is hereditary, Kirby and his wife, Tanya, are expecting twins who are free of the condition thanks to a new reproductive technology that prevents the passing on of life-threatening genetic conditions.

      Pre-implantation genetic diagnosis (PGD) involves the use of in vitro fertilization, through which medication stimulates the development of eggs in a woman’s ovaries. The eggs are removed and fertilized with sperm, and the resulting embryos develop in a laboratory. For PGD, a single cell is removed from each embryo and tested for the presence of a genetic abnormality. Results are available within two days, and only unaffected embryos are placed in the woman’s uterus.

      PGD is for people who carry the genes for serious inherited disorders such as Huntington’s disease (which involves sudden movements, unpredictable mood, and loss of intellectual abilities), thalassemia (a blood disorder), cystic fibrosis (a fatal multiorgan disease primarily affecting the lungs and digestive system), and Tay-Sachs disease, a lipid-storage disorder that leads to blindness, deafness, an inability to swallow, paralysis, and dementia.

      Kirby, whose heart is functioning at about 20 percent right now, can only walk about a block before becoming exhausted. He takes anti-arrhythmia medication and has an implantable cardioverter-defibrillator in his chest. He considers PGD a blessing.

      “I could not look at my child knowing that we could have stopped this disease,” Kirby told the Georgia Straight in a phone interview. “I didn’t want to put my child through what I’ve gone through.”¦I didn’t want to worry about our child every time she went outside to play.

      “I’m looking down the barrel of a heart transplant,” he added. “I didn’t want my child to ever have to go through that.”

      Dr. Al Yuzpe, cofounder and codirector of Vancouver’s Genesis Fertility Centre, which offers PGD, emphasized that the technology is strictly for use among couples who carry genes for serious diseases.

      “We’re not talking about minor things that change people’s physical appearance,” Yuzpe said in a phone interview. “We’re not in the designer-baby business. This is to eliminate significant diseases that are severely incapacitating or cause early death or demise.”

      He noted that other types of prenatal screening, such as chorionic villus sampling and amniocentesis, test for certain genetic conditions, but not until a woman is in her first and second trimester, respectively. Making a decision to terminate a pregnancy at those stages is “emotionally traumatic”, according to Yuzpe.

      PGD, he said, provides people with a tremendous sense of relief.

      “It takes a huge load off of these couples knowing that they will not be passing a significant condition to their children, or that their children will have the same problem and pass it on to their own kids.”

      Although it’s a boon to people like Kirby and his wife, not everyone embraces the procedure. Some disability-rights groups compare PGD to eugenics, with the selective elimination of embryos with imperfect traits being the ultimate form of prejudice. Because embryos that are found to carry a defective gene are destroyed, some religious organizations and anti-abortionists view the procedure as akin to abortion. From this perspective, interfering with the natural order means people are playing God.

      Holly Longstaff, a doctoral fellow with UBC’s independent interdisciplinary studies graduate program who did her PhD thesis on PGD, says that future health and social policy related to the technology must take into account the ethical considerations at the individual, family, and societal levels.

      “People have really compelling motivations to want to have PGD,” Longstaff said in a phone interview. “But then certain competing groups, such as people with disabilities, want society to recognize that using this technology is a discriminatory practice toward them.”¦Every argument is really compelling”¦and as a society, we have to consider all perspectives.”

      An analysis of issues around the genetic diagnosis of embryos published in the Canadian Medical Association Journal last year noted that loaded language has distorted public and scientific discourse.

      “The notions of ”˜eugenics’ and ”˜the perfect child’, in particular, are exercising undue influence on policy choices and thus limiting access to genetic diagnosis,” the authors wrote. “This choice of language confuses fiction with reality. It also risks miring the debate on pre-implantation genetic diagnosis in rhetorical quicksand.”

      In a technical update on PGD published in the August 2009 edition of the Journal of Obstetrics and Gynaecology Canada, the Society of Obstetricians and Gynaecologists of Canada made several recommendations. It advised, for instance, that couples considering the procedure should receive genetic counselling so that they clearly understand their risk of having an affected child, the impact of the disease on their offspring, and the benefits and risks of pre-implantation testing.

      The main limitation of PGD is the low success rate of in vitro fertilization. According to the SOGC, only 20 to 30 percent of couples conceive per IVF cycle, and the rate for those undergoing PGD is about the same.

      Cost is another obstacle to many couples: one IVF cycle plus PGD costs approximately $15,000, Yuzpe says. Neither PGD nor IVF treatments are covered by the government.

      Comments