Mitochondrial Replacement Therapy

See how to make a baby with 3 parents, a process called mitochondrial replacement therapy

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 in every 4,300 individuals in the US has mitochondrial disease

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.

Eight British children have been born via mitochondrial replacement therapy

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.)

3-parent baby approach may help women with infertility

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.

IVF procedures fertilize eggs outside the body in a laboratory dish

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 first child born via mitochondrial replacement therapy was born in 2016

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.

Australia legalized 3-parent IVF in 2022

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.

Four frozen embryos in the US were created via 3-parent IVF technique

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.)

3-parent IVF removes most—but not all—faulty mitochondria

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.)

3-parent baby technique fuels worries of future 'designer babies'

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.