Experiments using sperm and egg cells from three different people to make a single embryo are all right — if they are carefully monitored and regulated, expert advisers said Wednesday.
Such "three-parent" babies could be a way for people with a high risk of rare, devastating genetic diseases to have healthy children that are genetically their own, the National Academy of Medicine panel said.
The Food and Drug Administration should carefully regulate such experiments, the panel said in a report.
And at first, the panel advised, only male embryos should be made this way until it's clear that dangerous mutations would not be passed down to future generations.
"This will be an amazing breakthrough, benefiting patients who otherwise could not have healthy, genetically related children," said Dr. Owen Davis, president of the American Society for Reproductive Medicine.
The FDA asked the academy, formerly known as the Institute of Medicine, to look at the three-person embryo processes, called mitochondrial replacement techniques (MRT). These are variations of in vitro fertilization, or IVF — the method that creates so-called "test-tube babies."
The new techniques would be used to prevent the transmission of certain types of diseases that occur at the mitochondrial DNA level, the experts said.
In IVF, egg and sperm are united in a lab dish to make a fertilized egg that can grow first into a blastocyst and then an embryo.
MRT adds a step: The mother's nuclear DNA would be removed and placed into the egg cell of another woman. The father's sperm would then be used to fertilize that hybrid egg.
Any resulting embryo would mostly be the genetic child of the two parents but would get their 37 mitochondrial genes from the female egg donor.
Damaged mitochondria are responsible for more than 200 different diseases. They include Alpers disease, which causes seizures, dementia and blindness, and Leigh's disease, a progressive disorder in which brain cells gradually die off, causing a range of symptoms.
There's no cure for any of these conditions.
"MRT, if effective, could satisfy the desire of women to have a genetically related child without incurring the risk of passing on mitochondrial disease," the panel wrote.
But there are tricky scientific and ethical questions. Such babies could have what are known as germline changes, which can be passed down from generation to generation, making a lab mistake potentially the problem of people born decades later.
Then there's the issue of "playing God', the panel noted. "These concerns warrant significant caution and the imposition of restrictions rather than a blanket prohibition on the use of MRT," they concluded.
"Initial clinical investigations of mitochondrial replacement techniques (MRT) should be considered by the U.S. Food and Drug Administration (FDA) only if and when the following conditions can be met," they added.
The conditions include tests to establish safety, first using animals and then embryos that could never grow into babies, and that the disease being prevented is severe and that only male embryos are used.
Mitochondrial DNA is in the egg cell itself and is passed down unchanged from mother to child. Males do not pass along mitochondrial DNA.
Federal funds could probably not be used for these experiments, the committee noted.
"MRT would involve the creation, manipulation, and possible destruction of embryos not only in the preclinical research phase but also during clinical investigations and perhaps in clinical use," they wrote.
"While the creation of human embryos for research is not prohibited under federal law in the United States (although some states are more restrictive), neither FDA nor any other agency of the U.S. Department of Health and Human Services can financially support such research where embryos are destroyed, discarded, or subjected to risks with no prospect of medical benefit for the embryo."
Davis said: "We agree with the committee that the health and safety of the children born using these methods is of paramount concern and that initial clinical investigations should be limited to women at risk of transmitting serious mitochondrial disease to their children and that the children born from cycles using the procedure must be followed carefully."
Fertility specialist Dr. Jamie Grifo of New York University tried one mitochondrial IVF technique in the 1990s to help older women conceive healthy children using healthy eggs donated by younger women, but the FDA asked him to stop.
Mitochondria help provide energy in a cell. Mitochodrial DNA accounts for less than 1 percent of a person's genetic traits, but these functions are important to health.