The September 2016 birth of the first “three-parent baby” using mitochondrial replacement therapy showcased genetic engineering’s potential to eliminate inherited diseases while sparking designer baby fears.
The Technique
Mitochondrial replacement therapy combines DNA from three people: nuclear DNA from mother and father, plus healthy mitochondria from a donor woman. The mother carried mutated mitochondria causing Leigh syndrome (fatal neurological disorder killing most infants). By replacing her mitochondria with a donor’s, the baby inherited healthy cellular powerhouses.
The Baby
A Jordanian couple worked with U.S. physician John Zhang, who performed the procedure in Mexico (where regulations are lenient). The baby boy, born April 2016 and announced in September, was healthy with no signs of Leigh syndrome. The mitochondrial donor contributed less than 1% of total DNA - but that 1% passes to future generations.
UK Approval
The UK approved mitochondrial replacement in 2015, becoming the first country to legalize “three-parent babies.” The Human Fertilisation and Embryology Authority granted the first treatment licenses in 2017. By 2023, over 30 UK families had used the technique.
Ethical Debates
Critics called it genetic modification of the germ line - changes pass to children and grandchildren forever. “Designer baby” fears resurfaced - if we can swap mitochondria, why not select for height, intelligence, or appearance? Supporters argued mitochondria don’t affect traits like eye color or personality - only disease risk.
Germ-Line Editing
The technique differs from CRISPR genome editing but shares the controversy: modifying heritable DNA. Most nations ban germ-line editing. The 2018 CRISPR babies scandal intensified debates. Mitochondrial replacement seems more acceptable because it prevents severe disease, not enhancement.
Expanding Use
Australia approved the technique in 2022. The U.S. FDA banned it pending more research. Clinics in Ukraine and Greece offered it commercially. An estimated 1 in 5,000 people carry disease-causing mitochondrial mutations - thousands could benefit.
Source: New Scientist Three-Parent Baby