Although three-person IVF has similarities to cytoplasm transfer, the intent is different, Mathews said. Three-person IVF is not just about increasing the chances IVF will work, it's about creating a baby without a deadly disease.
"We certainly think about things differently in different contexts," Mathews said.
Options for Parents with Mitochondrial DNA Flaws
Mothers often don't know there's anything wrong with their mitochondrial DNA until they have a child with mitochondrial disease, said Dr. Mary Kay Koenig, a pediatric neurologist at the University of Texas Health Science Center at Houston. Koenig specializes in mitochondrial disease and oversees the center's Leigh's syndrome clinic, where she treats Will.
She said there are three options for parents at risk for passing on mitochondrial disease to their children: Take their chances and have another baby anyway, don't have any more children, or use an egg donor. But using an egg donor can be difficult and expensive and isn't an option for everyone, she said.
Most of Koenig's patients either opt to have no more children or take their chances. Those who take their chances often have more babies with different presentations of the same mitochondrial disease.
"I see families who have five and six siblings all affected by mitochondrial disease," she said.
To Koenig, the three-person IVF that's been proposed in the United Kingdom isn't about "designer babies."
"In my opinion, this doesn't fit in," she said. "A lot of people see that as genetic selection, but it's really about people being responsible… They're not asking us to pick a girl or a boy, blond hair or brown hair. They're just asking us to pick whether or not that child has Leigh's syndrome."
Martins Expanding Their Family
It took Martin two years, but she's finally pregnant with her second child after undergoing IVF with a donor egg. The baby won't have her genetic material, but it will have her husband's genes and no mitochondrial disease.
No one is happier than the baby's soon-to-be big brother, Will.
"If you ask him, 'Are you gonna have a baby brother or sister?' he'll very emphatically and authoritatively say 'boy' or 'brother,'" Martin said, adding that she has no idea whether the baby is a boy or a girl. "He's as excited as a 4-year-old can get about something he probably doesn't really grasp."
It isn't three-person IVF, but Martin said there's still something empowering about leaving her mitochondrial flaws behind.
"There will not be another child from our family to have this exact gene," she said. "It's kind of exciting to stop something so terrible from ever occurring again."