The use of the controversial procedure continues despite medical risks and ethical concerns.
In early January, a mother in Ukraine gave birth to a baby girl with DNA from three parents—two women and one man. She is the second baby known to be born from modern mitochondrial replacement therapy (MRT), but her birth is a first in several other ways.
Proponents initially touted MRT as a remedy to allow women with serious mitochondrial disease—genetic defects in the mitochondrial DNA that are passed down to their children—to have healthy babies. But this is the first use of MRT as a fertility treatment for a couple without any known genetic disease. A Ukrainian doctor used the procedure after conventional in vitro fertilization had not been successful.
This is also the first time this particular type of MRT, called pronuclear transfer, has successfully produced a baby. In this procedure, doctors remove the nucleus from two embryos, one from the parents and one from a donor egg that has been fertilized with the father’s sperm. They then transfer the nucleus from the parent’s embryo into the de-nucleated donor embryo and implant it in the mother.
Even among proponents of MRT, this particular birth has stirred controversy because of the baby’s gender. Researchers previously recommended that MRT be used only to create boy babies. Boys are much less likely to pass on any genetic modifications to their offspring. Once the sperm and egg come together to form an embryo, the mitochondria from the father dies, leaving only the mother’s mitochondria.
But the recent procedure in Ukraine did not produce a “suitable male embryo,” Valery Zukin, the doctor who performed the procedure, told CNN. With the approval of the parents and a medical review board, he decided to implant a female embryo.
When scientists first developed MRT, some ethicists warned that if it became legal it would soon be used for everything from treating infertility to creating designer babies, not just for cases of mothers with mitochondrial disease. It appears they were right.
“We are accelerating down a slippery slope now when we are going to manufacture children in the laboratory to specific genetic characteristics,” said David Prentice, a bioethicist and the vice president and research director at the Charlotte Lozier Institute.
But even if doctors confine the use of MRT to only cases of genetic diseases, the ethical concerns don’t disappear. This technique is not easy to do, Prentice said: “It’s a matter of trial and error. Likely many embryos were destroyed in the process before this little girl made it to birth.”
MRT also carries inherent health risks for the child, said Arina Grossu, director of the Family Research Council’s Center for Human Dignity. “Scientists also don’t know yet what kind of irreparable impact tinkering with the human genome will have on this child and future generations. It is contrary to human dignity to treat the creation and destruction of human life as a science experiment,” she said.
Researchers recently discovered MRT cannot guarantee mitochondrial disease will not be passed on to the baby. The procedure does not eliminate every single bit of the mother’s mitochondria, and a small amount is transferred to the donor embryo. A recent study published in the journal Nature showed that even a tiny amount of the mother’s mitochondria can replicate faster than the donor’s mitochondria and can become dominant, potentially spreading the disease to the child.
Despite the risks and ethical concerns, doctors are likely to move forward with the technique. Zukin told CNN he has a second patient in a similar situation who is expecting to give birth in early March. Although no three-parent babies have yet been born in Britain, the United Kingdom has approved the procedure for women with mitochondrial disease. MRT has not been approved in the United States, but last year a U.S. physician traveled to Mexico, where the procedure is legal, and used a type of MRT to produce a baby boy.
Prentice is thankful there is at least a temporary prohibition in the United States but said he thinks “this needs to be made a permanent, and frankly global, prohibition.”
— by Julie Borg