Mitochondrial donation is an advanced form of assisted reproductive treatment designed to help some families avoid passing serious mitochondrial diseases from mother to child.
You may have heard it described in news reports as “three-parent IVF” or the creation of “three-parent babies.”
Those phrases attract attention, but they can also give a misleading impression of what the treatment actually involves.
The proper term is mitochondrial donation treatment (MDT).
The United Kingdom became the first country in the world to establish a regulatory system allowing mitochondrial donation for carefully selected patients at high risk of transmitting serious mitochondrial disease.
A decade after the UK's regulations were approved, researchers reported an important milestone: eight babies had been born in the UK following mitochondrial donation treatment.
So what exactly is mitochondrial donation, why is it needed, and does a child born following the treatment really have three parents?
What Are Mitochondria?
Mitochondria are tiny structures found inside almost all human cells.
They perform a crucial function: producing much of the energy cells need to work properly.
For this reason, mitochondria are sometimes informally described as the “powerhouses” of cells.
Unlike most structures within cells, mitochondria contain a small amount of their own genetic material known as mitochondrial DNA, or mtDNA.
Most of a person's DNA is located within the nucleus of the cell.
Mitochondrial DNA represents only a very small proportion of a person's total genetic material.
How Is Mitochondrial DNA Inherited?
Mitochondrial DNA is normally inherited from the mother.
This means that a woman carrying certain disease-causing mitochondrial DNA variants may pass them to her children.
The amount of affected mitochondrial DNA transmitted can vary, which means predicting how severely a child may be affected can sometimes be difficult.
What Is Mitochondrial Disease?
Mitochondrial diseases are a diverse group of genetic disorders that interfere with mitochondria's ability to produce the energy cells need.
Because virtually every organ requires energy, mitochondrial disorders can affect many different parts of the body.
Depending on the particular disorder, symptoms can involve the:
- brain
- nervous system
- muscles
- heart
- eyes
- ears
- liver
- kidneys.
Some people experience relatively mild disease, while others develop severe, progressive and potentially life-threatening illness.
There is currently no universal cure for mitochondrial disease.
Treatment generally focuses on managing symptoms and complications.
Why Was Mitochondrial Donation Developed?
For some women carrying harmful mitochondrial DNA variants, conventional reproductive options may not reliably prevent transmission to a child.
Mitochondrial donation was developed to reduce that risk.
The basic concept is to combine:
- the intended mother's nuclear DNA
- sperm from the intended father or sperm provider
- healthy mitochondria from a donor egg.
The resulting embryo therefore contains nuclear genetic material from the intended parent or parents together with a small amount of mitochondrial genetic material from the egg donor.
Does This Really Create a “Three-Parent Baby”?
This is where the popular terminology can be misleading.
A child born following mitochondrial donation does receive DNA from three people.
However, the contributions are very different.
The overwhelming majority of the child's genetic material comes from the nuclear DNA of the intended mother and father—or other sperm provider where applicable.
The mitochondrial donor contributes healthy mitochondrial DNA.
Mitochondrial DNA contains genes involved primarily in mitochondrial energy production and represents only a very small fraction of the child's total DNA.
The donor does not contribute the nuclear chromosomes that contain most of the genes involved in a person's inherited biological characteristics.
For this reason, “three-parent baby” is a media shorthand rather than a precise scientific description.
How Does Mitochondrial Donation Work?
Two mitochondrial donation techniques have been authorised under UK law:
- Maternal spindle transfer (MST)
- Pronuclear transfer (PNT)
Both aim to produce an embryo containing the intended mother's nuclear genetic material while greatly reducing the amount of potentially harmful mitochondrial DNA.
What Is Maternal Spindle Transfer?
Maternal spindle transfer occurs before fertilisation.
The mother's nuclear genetic material is removed from her egg.
Nuclear genetic material is also removed from a healthy donor egg, leaving the donor's healthy mitochondria behind.
The mother's nuclear material is then transferred into the donor egg.
That reconstructed egg can subsequently be fertilised with sperm.
The resulting embryo therefore contains:
- nuclear DNA from the intended mother
- nuclear DNA from the sperm provider
- healthy mitochondrial DNA primarily from the egg donor.
What Is Pronuclear Transfer?
Pronuclear transfer occurs after fertilisation has begun.
An egg from the intended mother and an egg from a mitochondrial donor are fertilised.
The nuclear genetic material from the embryo created using the intended mother's egg is transferred into the donor-derived embryo after the donor embryo's nuclear material has been removed.
The reconstructed embryo therefore retains the intended parents' nuclear genetic material while containing predominantly healthy donor mitochondria.
Why Did the UK Change the Law?
The UK spent years evaluating mitochondrial donation through scientific reviews, public consultation, ethical discussion and parliamentary debate.
In February 2015, Parliament approved regulations allowing maternal spindle transfer and pronuclear transfer for the purpose of avoiding serious mitochondrial disease.
The Human Fertilisation and Embryology (Mitochondrial Donation) Regulations 2015 came into force on 29 October 2015.
The UK consequently became the first country to establish a regulated system permitting these mitochondrial donation techniques for clinical treatment.
What Happened in December 2016?
At that time, the UK's Human Fertilisation and Embryology Authority (HFEA) had just decided that mitochondrial donation could be introduced cautiously in specific circumstances following further scientific review.
But that did not mean babies had already been born in the UK through the treatment.
Clinics still needed appropriate licensing, and individual patients subsequently required regulatory approval.
What Happened Next?
In March 2017, the HFEA approved the first clinic application for mitochondrial donation treatment at Newcastle Fertility Centre at Life.
Individual patients then had to receive separate approval before treatment could proceed.
The programme developed cautiously because mitochondrial donation was a new reproductive technology requiring careful monitoring.
The Major 2025 Development
In July 2025, researchers published peer-reviewed results describing children born through the UK's mitochondrial donation programme.
The research reported eight babies born following mitochondrial donation treatment.
According to the HFEA and the published research, all eight children were healthy at birth and had either undetectable or low levels of the disease-associated mitochondrial DNA variants in blood.
At the time of publication, all of the children were reported to be making normal developmental progress.
These results provided the first peer-reviewed evidence of births through the UK's regulated mitochondrial donation programme.
Does That Mean the Treatment Has No Risks?
No.
Eight births represent an encouraging but still relatively small body of evidence.
Mitochondrial donation remains a highly specialised treatment, and continued follow-up is important.
In the 2025 published results, researchers reported some medical conditions among the children.
One child developed abnormal blood lipid levels and a heart rhythm problem; both responded to treatment. The child's mother had experienced abnormal lipid levels during pregnancy.
Another child developed infantile myoclonic epilepsy, which later resolved spontaneously.
Researchers did not establish that these conditions were caused by mitochondrial donation.
This distinction is important.
When evaluating a new reproductive treatment, scientists need larger numbers and longer follow-up before uncommon or long-term risks can be understood confidently.
What Is Mitochondrial DNA Carryover?
One challenge with mitochondrial donation is that transferring the mother's nuclear genetic material may also unintentionally transfer a small amount of her mitochondria.
This is called mitochondrial DNA carryover.
The aim is to keep the amount of potentially harmful maternal mitochondrial DNA as low as possible.
Researchers therefore monitor children born following treatment to understand how mitochondrial DNA levels behave over time.
Can Harmful Mitochondrial DNA Increase Again?
Potentially.
Researchers have been interested in a phenomenon sometimes described as reversion, in which the proportion of maternal mitochondrial DNA may increase in some cells after mitochondrial donation.
This does not mean every child will experience it.
However, it is one reason why mitochondrial donation continues to be carefully studied and why long-term follow-up remains valuable.
Who Can Receive Mitochondrial Donation in the UK?
Mitochondrial donation is not a general IVF treatment.
In the UK, it is intended for people at very high risk of passing serious mitochondrial disease to their children.
Each treatment application is assessed individually by the HFEA according to legal requirements.
It is therefore not available simply because someone wants to improve IVF success rates or select particular characteristics in a child.
Is Mitochondrial Donation Used to Create “Designer Babies”?
No.
The UK's mitochondrial donation regulations restrict the treatment to preventing or reducing the risk of transmitting serious mitochondrial disease.
The treatment is not authorised as a method for choosing characteristics such as:
- intelligence
- height
- eye colour
- athletic ability
- personality.
Mitochondrial donation should therefore not be confused with genetic enhancement.
Does Mitochondrial Donation Edit a Baby's Genes?
Mitochondrial donation is also different from gene-editing technologies such as CRISPR.
The authorised UK procedures involve transferring nuclear genetic material between eggs or embryos so that the resulting embryo contains predominantly healthy donor mitochondria.
They do not work by directly rewriting particular DNA sequences in the way gene-editing technologies are designed to do.
Can Changes Be Passed to Future Generations?
This issue is scientifically and ethically important.
Mitochondrial DNA is maternally inherited.
Therefore, a girl born following mitochondrial donation could potentially pass donor-derived mitochondrial DNA to her own children.
This heritable aspect of mitochondrial donation was one of the reasons the technology received extensive ethical and regulatory scrutiny before being permitted.
Who Regulates the Treatment in the UK?
The Human Fertilisation and Embryology Authority (HFEA) regulates fertility treatment and embryo research in the UK.
Clinics cannot simply decide to offer mitochondrial donation independently.
They require appropriate HFEA licensing.
Individual treatment cases must also satisfy regulatory requirements.
As of the HFEA's July 2025 update, 35 patients had been approved for mitochondrial donation treatment, and the published research reported that 25 patients had undergone pronuclear transfer.
Where Is Mitochondrial Donation Performed in the UK?
According to the HFEA, Newcastle Fertility Centre at Life is currently the UK clinic licensed to conduct research and treat patients using mitochondrial donation techniques.
People considering the treatment require specialist assessment.
Is Mitochondrial Donation Available Worldwide?
Laws and regulations governing mitochondrial donation vary considerably between countries.
The UK was the first country to create a specific regulatory framework permitting clinical mitochondrial donation.
Other countries have taken different regulatory approaches.
For example, Australia subsequently introduced legislation allowing a staged approach to mitochondrial donation research and clinical development.
Anyone considering reproductive treatment should therefore obtain current information from the appropriate health and fertility regulator in their own country.
What Are the Ethical Concerns?
Mitochondrial donation has generated considerable ethical discussion.
Concerns have included:
- uncertainty about very long-term health outcomes
- genetic changes that can potentially pass to future generations
- the welfare of children born through new reproductive technologies
- how mitochondrial donors should be understood legally and socially
- concerns about where boundaries should be drawn around future genetic technologies.
These are legitimate subjects for continued scientific and ethical discussion.
However, mitochondrial donation should be evaluated according to what the treatment actually does rather than assuming it allows unrestricted genetic modification.
Why Do Families Consider the Treatment?
For families affected by severe inherited mitochondrial disease, reproductive decisions can be extremely difficult.
Some people face a substantial risk of having a child with a serious, disabling or life-threatening condition.
Mitochondrial donation offers certain eligible families another reproductive option that may allow them to have a genetically related child while substantially reducing the risk of transmitting harmful mitochondrial DNA.
It is not suitable for everyone.
Specialist genetic and fertility counselling is therefore an important part of decision-making.
What Have We Learned Since 2016?
When this article was originally published in December 2016, mitochondrial donation was still moving from scientific research toward carefully regulated clinical treatment in the UK.
We now know considerably more.
The UK established a licensing system.
Newcastle received approval to provide treatment.
Individual patients received regulatory approval.
And, most importantly, peer-reviewed research published in 2025 reported eight babies born following mitochondrial donation treatment.
Those early results are encouraging, but researchers and regulators continue to emphasise careful monitoring because the number of children remains small and long-term evidence is still developing.
The Bottom Line
Mitochondrial donation is a specialised reproductive treatment designed to reduce the risk that a woman with certain serious mitochondrial DNA disorders will pass the disease to her children.
The treatment combines nuclear genetic material from the intended parent or parents with healthy mitochondria from a donor egg.
Although this has led to the popular phrase “three-parent baby,” the expression can be misleading because the mitochondrial donor contributes only a small portion of the child's overall DNA and does not contribute the nuclear genome.
The UK became the first country to establish a regulated clinical pathway for mitochondrial donation.
In 2025, researchers reported eight babies born through the UK's programme, all healthy at birth and making normal developmental progress at the time reported.
These results represent an important milestone, but mitochondrial donation remains a highly specialised treatment requiring careful regulation, individual assessment and continued long-term research.
Medical Disclaimer
This article provides general educational information and does not replace personalised medical, genetic or fertility advice. Mitochondrial diseases and reproductive treatment options are complex, and eligibility for mitochondrial donation depends on individual circumstances and local regulations. Anyone affected by mitochondrial disease or concerned about passing an inherited disorder to a child should consult appropriately qualified genetics and reproductive-medicine professionals.
Sources and Further Reading
Human Fertilisation and Embryology Authority — Mitochondrial Donation Treatment
https://www.hfea.gov.uk/treatments/embryo-testing-and-treatments-for-disease/mitochondrial-donation-treatment/
HFEA — Eight Babies Born After Mitochondrial Donation Treatment
https://www.hfea.gov.uk/about-us/news-and-press-releases/2025/hfea-comments-on-the-news-that-eight-babies-have-been-born-after-mitochondrial-donation-treatment
HFEA — World First as Mitochondrial Donation Regulations Come Into Force
https://www.hfea.gov.uk/about-us/news-and-press-releases/2015/world-first-as-mitochondrial-donation-regulations-come-into-force/
UK Government — Human Fertilisation and Embryology (Mitochondrial Donation) Regulations 2015
https://www.gov.uk/government/publications/impact-assessment-opinion-the-human-fertilisation-and-embryology-mitochondrial-donation-regulations-2015
New England Journal of Medicine — Mitochondrial Donation in a Reproductive Care Pathway for mtDNA Disease
https://www.nejm.org/doi/full/10.1056/NEJMoa2503658
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