Mitochondrial replacement therapy—which first led to a healthy child's birth in 2016—aims to help parents avoid rare mitochondrial diseases passed from mother to child by eliminating a mother's faulty mitochondrial DNA. It swaps in the mitochondrial DNA of an unaffected female donor either before or after fertilization. This lab-based approach has also garnered interest for infertility, since dysfunctional mitochondria may be a factor in female infertility.
Sometimes referred to as "three-parent IVF" because it's a modified in vitro fertilization process, this reproductive technique creates an embryo by integrating genetic material from a mother, a father, and a mitochondrial DNA donor. The donor's egg is tapped for this process, but it will contain the nuclear DNA of the biological mother.
Although almost all our genes reside in the nucleus of our cells, a tiny portion—37 genes—reside in mitochondria, the powerhouse of cells, and mitochondrial DNA, or mtDNA, is almost always passed along the maternal line, from mother to offspring. There are several hundred mitochondrial diseases in which the mitochondria do not perform as expected, affecting between 1,000 and 4,000 kids in the US each year.
Healthy babies have already been born using this approach, including eight in the United Kingdom. But recent research suggests that faulty mitochondrial DNA may sometimes persist after this intervention, even if almost all the mother's mitochondrial DNA is removed. That faulty DNA, even in tiny amounts, can potentially result in babies or future generations at risk of developing severe mitochondrial diseases, including ones that are fatal or cause severe organ damage.
Hours of research by our editors, distilled into minutes of clarity.
This primer video dives into the science of mitochondrial disease risks, how this controversial mitochondrial replacement technique can work, and why proponents say this reproductive advance—already legalized in the UK and Australia—is needed in the United States.
Roughly 1,000 to 4,000 kids are born with these conditions each year in the US though many of the diseases are fatal. Mitochondrial disorders often affect the organs that require the most energy, including the heart, brain, and muscles.
In July 2025, a decade after British lawmakers signed off on allowing three-parent IVF, scientists announced that eight healthy babies had already been born using this approach. The news was included in a pair of research articles published in a peer-reviewed journal that noted the oldest kids were already more than two years old, and that they were hitting developmental milestones as expected. (Some users may encounter a paywall.)
Though the topline promise of this approach is avoiding passing on mitochondrial diseases, some researchers and companies have been eyeing its potential for helping with female infertility, since faculty mitochondria may contribute to the condition. Recent research suggests this approach could be promising.
In vitro fertilization is a complex and expensive set of procedures that potential parents dealing with infertility or genetic disorders may turn to when other methods are unavailable. IVF births account for 2% to 3% of all live births in the US annually.
The healthy baby boy's mother carried genes for a rare mitochondrial disease called Leigh syndrome and after multiple miscarriages the family opted to try the controversial procedure. It was conducted by a US doctor in Mexico. The procedure is prohibited in the United States.
It was the second country, after the UK, to legalize the procedure, which is still prohibited in the US. There are more than 300 rare mitochondrial diseases that can be passed from a mother to her offspring.
Columbia University researchers created four embryos using mitochondrial replacement therapy for four female patients who didn't want to pass on mitochondrial diseases to their children. Yet US law restricts the researchers from implanting the embryos so they remain frozen. (Some users may encounter a paywall.)
The process scoops out about 99% of the mother's mitochondrial DNA—replacing it with that of a donor woman—but because that roughly 1% is still in the system there is still a small chance of disease for the resulting child or future generations. (Some users may encounter a paywall.)
Some critics of this approach worry that any genetic manipulation will both culturally and technologically normalize the idea of "designer babies"—embryos that are manipulated or selected based on physiological characteristics including height, eye color, athletic ability, and intelligence.
Discover a broad spectrum of topics, from fundamental anatomy to the latest in medical research and treatments, all aimed at enhancing your understanding of health, wellness, and our bodies. Our resources are meticulously curated to offer precise and pertinent information to students, professionals, and anyone interested in learning more about the medical sciences. Dive in to stay informed, make well-informed health decisions, and explore the intriguing world of medicine.