By Dr. Charles Debrovner
Most people spend much of their adult lives trying not to have children. During the past fifty years, the ability to make reproductive decisions has expanded significantly to include a wide variety of family planning options. However, when we do want to have children, and conceiving or carrying a pregnancy proves difficult or impossible, we become frustrated, angry, and depressed. This is because we have grown up believing that we will be able to have children when we are ready and willing, passing on our traits, values, and ideals.
Fortunately, medical advancements have provided us with a number of options for solving infertility problems. A major breakthrough came with the perfection of in-vitro fertilization (IVF). The IVF process has helped us surmount many obstacles, including a couple’s predisposition to genetic problems and the risk an older woman has of conceiving a child with Down’s syndrome. Pre-implantation genetic diagnosis allows fertilized eggs to be tested for defective genes and chromosomes; only embryos that are deemed healthy are approved for implantation. Sometimes, however, healthy embryos cannot be created; in these instances, women have the option of using donor eggs. Donors are usually young healthy women who have similar traits to the prospective mother. However, recent breakthroughs might make this method of IVF unnecessary in some cases.
Embryos have 46 chromosomes – 23 come from the egg and 23 come from the sperm. These chromosomes contain the thousands of genes that are responsible for producing a person’s unique traits. A recent discovery revealed that additional genes are located in the mitochondria of cells; mitochondria are responsible for converting the energy from food into a form of fuel that cells can use. If mitochondrial genes do not function normally, they prevent the embryo from developing properly and can cause problems for the child after he or she is born.
Scientists have developed two techniques that can be incorporated into the IVF process to prevent mitochondria-related problems from occurring. These techniques allow the embryo to have the trait-producing nuclear chromosomes of the parents, but replace defective mitochondria with healthy, donated mitochondria.
An embryo’s mitochondria come from the egg. One of the aforementioned techniques involves obtaining a donor egg with healthy mitochondria; the other modifies the embryo post-fertilization. Researchers currently have no reason to believe that one technique is better than the other.
Earlier this year, both houses of Parliament in the United Kingdom approved these techniques. Additionally, researchers at the Saint Barnabas Medical Center in New Jersey and a medical group in California have reported that, as part of their research with mitochondrial transfer, 30 children have been born to previously infertile couples and are doing well. The FDA has not yet approved these techniques for non-research use in this country, but many hope that the US will follow the UK in doing so.
Some scientists worry about potential, currently undetectable problems that might occur if donor mitochondria are passed on to future generations. Others point out, however, that there might be as yet undetected problems associated with donated ova, the current solution to mitochondria-related problems. But donor eggs contain between 20,000 – 25,000 genes, while mitochondria contain only 13 to 37 genes; thus, donor mitochondria appear to be less likely to lead to unforeseen complications.
Additionally, some ethicists are concerned that these techniques are the first step down a slippery slope toward cloning. But this worry is misplaced – cloning uses a somatic cell to create a new individual that is an exact genetic duplicate of the donated cell, and the techniques we have been discussing do not modify any of the physical traits of the embryo, they simply replace defective mitochondria to produce effective and healthy energy processes. These techniques provide a specific solution to a specific infertility problem – they should be welcomed as an advancement in reproductive technology, not rebuffed as a precursor to cloning.
