People who want children but who have a debilitating disease can face an agonizing question: Will they genetically pass on their disease to offspring?
Washington University reproductive endocrinologists and fertility specialists at Barnes-Jewish Hospital have become a regional resource for patients with single-gene disorders who want pre-implantation genetic diagnosis (PGD) to help them address this risk. The test also is recommended if a couple already has a child with a single-gene disorder.
PGD evaluates embryo DNA before in-vitro fertilization (IVF) to identify those embryos that have not inherited a single-gene mutation. Recent single-gene PGD testing at Barnes-Jewish Hospital has revealed the following diseases:
- Cystic fibrosis
- Fragile X syndrome
- Huntington’s disease
- Muscular dystrophy
- Sickle cell disease
“Many patients who carry a mutation for one of these diseases want to ensure their offspring won’t inherit their disorder,” says Kenan Omurtag, MD, a reproductive endocrinologist specializing in infertility and in-vitro fertilization. “The purpose of PGD is not to create designer babies; rather, it is an effective way to safely identify embryos that are free of single-gene mutations so they can be implanted via IVF and brought to term.”
People with a single-gene mutation face a significant risk that offspring will develop a single-gene disorder, Omurtag says. For example, two parents who are carriers of the cystic fibrosis gene mutation have a 1-in-4 chance of having a child who will develop the disease. And two parents who carry the sickle cell trait have a 1-in-4 chance of having a child who develops sickle cell anemia. A woman diagnosed with muscular dystrophy has a 50 percent risk of passing the disease on to her son; her daughter has the same risk of inheriting the mutation and becoming a carrier, thereby impacting the next generation of offspring.
Extracting DNA from an embryo for pre-implantation testing requires a great deal of expertise. “Our laboratory has been performing PGD for more than 10 years, and our embryologists have more than 20 years of combined experience with this technique,” Omurtag says. The biopsy typically takes place at five days post fertilization. Called a trophectoderm biopsy, the procedure extracts extra-embryonic tissue—material that will not be part of the developing fetus—for DNA testing. Embryos are frozen while the extracted tissue is analyzed. Embryos without mutations are then selected for implantation via IVF.
Expertise in IVF
One-third of women over the age of 35 will have difficulty achieving a pregnancy. Using data compiled in 2013, the Centers for Disease Control and Prevention (CDC) published a 2015 report on assisted reproductive technology (ART) success rates. The report indicates that an estimated 6.9 million women in the United States have received infertility services at some point in their lives.
According to the same CDC report, of those couples starting ART procedures in 2013, 29 percent went on to achieve a live birth. Omurtag says the team of reproductive endocrinologists at Barnes-Jewish Hospital has a 53 percent IVF success rate after one treatment cycle.
“IVF doesn’t guarantee a baby,” Omurtag says. “And patients sometimes have to undergo more than one IVF cycle. The process can be time-consuming?and it often takes an emotional toll that is magnified when a patient also is worried about the risk of passing on a debilitating or life-threatening disease.”
Pre-implantation genetic testing can ease some of that stress. At Barnes-Jewish Hospital, patients using PGD have access to genetic counselors working within the Division of Reproductive Endocrinology and Infertility and to obstetricians specializing in high-risk pregnancies. In total, the team represents the largest board-certified infertility specialty team in the region, and it was the first in Missouri to achieve successful in-vitro fertilization resulting in a live birth.
“We are here to evaluate, counsel and treat patients who need the most current fertility treatments, including IVF,” Omurtag says. “And for those who have a diagnosis or a strong family history of a single gene disorder, we can offer PGD to reduce their risk of having an affected offspring.”