Healthy babies born with DNA from three different people

Eight babies have been born in Britain through a pioneering reproductive method known as mitochondrial donation. This experimental technique uses DNA from three different individuals – a mother, a father, and a female donor – to help prevent the transmission of rare but potentially life-threatening genetic conditions from parents.

These conditions are caused by defective mitochondria, which are passed from mother to child and can lead to serious health problems like seizures, muscle weakness, or organ failure.

By replacing the faulty mitochondria with healthy ones from a donor, scientists created embryos less likely to inherit these devastating disorders. The result was the birth of eight healthy babies, marking a major advance in fertility science.

These children are not only medically significant but also symbolize new hope for families who carry mitochondrial diseases. For many such families, this development offers a safe and promising path to having healthy children, something that once seemed out of reach.

Why some need three-parent DNA

While most DNA sits in the nucleus, mitochondria have their own DNA. Mothers pass this small portion to children. If it’s faulty, it can cause devastating diseases.

Symptoms range from seizures and muscle weakness to organ failure and even death. These conditions are rare but life-altering.

Doctors use genetic testing during IVF to screen embryos. But sometimes, the results are unclear. For high-risk cases, researchers developed a backup plan – swap out the mother’s defective mitochondria with healthy ones from a donor.

Donor DNA from a third parent

This method is called pronuclear transfer. Eggs from both the mother and a donor are fertilized with sperm. After about ten hours, scientists remove the nucleus – the main genetic material – from both.

Then they insert the mother’s nucleus into the donor egg. This results in an embryo with nuclear DNA from the parents and healthy mitochondria from the donor.

The amount of donor DNA is tiny – less than 1%. The child will not have any traits from the donor.

A shift in global reproductive options

“Expanding the range of reproductive options will empower more couples to pursue safe and healthy pregnancies,” noted Dr. Zev Williams from Columbia University.

The UK approved this technique in 2015, changing the law in 2016 to allow clinical use. Australia also permits it. The U.S. currently does not.

Newcastle University and Monash University tested this method on 22 patients. Eight babies were born healthy. One woman is still pregnant. One baby showed higher abnormal mitochondria levels but remained disease-free. Experts continue to monitor them.

Who needs three-parent DNA?

Dr. Andy Greenfield from Oxford called the work “a triumph of scientific innovation.” He emphasized it will only help a small group. Most families can rely on early-stage embryo testing instead. But when that doesn’t work, pronuclear transfer could be the only path forward.

Robin Lovell-Badge from the Francis Crick Institute noted that this approach adds only a trace of donor DNA. “If you had a bone marrow transplant from a donor … you will have much more DNA from another person,” he said.

Safety, ethics, and regulation

The UK’s fertility regulator must approve every case. So far, 35 patients have received permission. In the U.S., Congress blocks FDA applications involving genetic modification of embryos.

“Whether that will change remains uncertain and will depend on evolving scientific, ethical, and policy discussions,” Williams said.

Critics worry that using DNA from three parents could have unforeseen consequences for future generations. Advocates argue that with careful regulation and continued research, the risks of three-parent techniques can be minimized.

Real families, real impact

Liz Curtis lost her daughter Lily to mitochondrial disease at just eight months old. “It turned our world upside down,” she recalled.

Liz founded the Lily Foundation to support affected families and research. “It’s super exciting for families that don’t have much hope in their lives,” she said.

Bobby McFarland, who helped develop the approach, noted that around 1 in 5000 people carry defective mitochondria.

McFarland treated 19 women with over 80% faulty mitochondria. Seven became pregnant, and one even had twins. In most of the newborns, no harmful mitochondrial DNA was found. Others had low, non-threatening levels.

What lies ahead for three-parent children

The babies continue to develop normally. Some faced health issues like high blood fat or epilepsy, but these were treated or resolved. Researchers will track the children long term to understand any delayed effects.

As science advances, this three-parent method could give new life to families facing genetic challenges. For now, it remains a carefully controlled yet groundbreaking option.

The study is published in the New England Journal of Medicine.

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