Associated Press
LONDON 鈥 Eight healthy babies were born in Britain with the help of an experimental technique that uses DNA from three people to help mothers avoid passing devastating rare diseases to their children, researchers said.
Rosie and Katie Merritt, of England, hold their sister, Lily, who died of a mitochondrial disease in 2006 at 8 months old.
Most DNA is found in the nucleus of our cells, and it鈥檚 that genetic material 鈥 some inherited from mom, some from dad 鈥 that makes us who we are. But there鈥檚 also some DNA outside of the cell鈥檚 nucleus, in structures called mitochondria. Dangerous mutations there can cause a range of diseases in children that can lead to muscle weakness, seizures, developmental delays, major organ failure and death.
Testing during the in vitro fertilization process can usually identify whether these mutations are present. But in rare cases, it鈥檚 not clear.
A nuclear genome from an egg carrying a mitochondrial DNA mutation is inserted into an egg donated by an unaffected woman.
Researchers have been developing a technique that tries to avoid the problem by using the healthy mitochondria from a donor egg. They reported in 2023 that the first babies were born using this method, where scientists take genetic material from the mother鈥檚 egg or embryo, which is then transferred into a donor egg or embryo that has healthy mitochondria but the rest of its key DNA removed.
People are also reading…
The latest research 鈥渕arks an important milestone,鈥 said Dr. Zev Williams, who directs the Columbia University Fertility Center and was not involved in the work. 鈥淓xpanding the range of reproductive options 鈥 will empower more couples to pursue safe and healthy pregnancies.鈥
Using this method means the embryo has DNA from three people 鈥 from the mother鈥檚 egg, the father鈥檚 sperm and the donor鈥檚 mitochondria 鈥 and it required a 2016 U.K. law change to approve it. It is also allowed in Australia but not in many other countries, including the U.S.
Experts at Britain鈥檚 Newcastle University and Monash University in Australia reported in the New England Journal of Medicine on Wednesday that they performed the new technique in fertilized embryos from 22 patients, which resulted in eight babies that appear to be free of mitochondrial diseases. One woman is still pregnant.
One of the eight babies born had slightly higher than expected levels of abnormal mitochondria, said Robin Lovell-Badge, a stem cell and developmental genetics scientist at the Francis Crick Institute who was not involved in the research. He said it was still not considered a high enough level to cause disease, but should be monitored as the baby develops.
Dr. Andy Greenfield, a reproductive health expert at the University of Oxford, called the work 鈥渁 triumph of scientific innovation,鈥 and said the method of exchanging mitochondria would be used only for a small number of women for whom other ways of avoiding passing on genetic diseases, like testing embryos at an early stage, was not effective.
Dave Merritt and Liz Curtis, of England, hold their daughter, Lily, who died of a mitochondrial disease in 2006 at 8 months old.聽
Lovell-Badge said the amount of DNA from the donor is insignificant, noting that any resulting child would have no traits from the woman who donated the healthy mitochondria. The genetic material from the donated egg makes up less than 1% of the baby born after this technique.
鈥淚f you had a bone marrow transplant from a donor 鈥 you will have much more DNA from another person,鈥 he said.
In the U.K., every couple seeking a baby born through donated mitochondria must be approved by the country鈥檚 fertility regulator. As of this month, 35 patients have been authorized to undergo the technique.
Critics have previously raised concerns, warning that it鈥檚 impossible to know the impact these sorts of novel techniques might have on future generations.
鈥淐urrently, pronuclear transfer is not permitted for clinical use in the U.S., largely due to regulatory restrictions on techniques that result in heritable changes to the embryo,鈥 Williams, of Columbia, said in an email. 鈥漌hether that will change remains uncertain and will depend on evolving scientific, ethical, and policy discussions.鈥
For about a decade, Congress has included provisions in annual funding bills banning the Food and Drug Administration from accepting applications for clinical research involving techniques, 鈥渋n which a human embryo is intentionally created or modified to include a heritable genetic modification.鈥
But in countries where the technique is allowed, advocates say it could provide a promising alternative for some families.
Liz Curtis, whose daughter Lily died of a mitochondrial disease in 2006, now works with other families affected by them. She said it was devastating to be told there was no treatment for her 8-month-old baby and that death was inevitable.
She said the diagnosis 鈥渢urned our world upside down, and yet nobody could tell us very much about it, what it was or how it was going to affect Lily.鈥 Curtis later founded the Lily Foundation in her daughter鈥檚 name to raise awareness and support research into the disease, including the latest work done at Newcastle University.
鈥淚t鈥檚 super exciting for families that don鈥檛 have much hope in their lives,鈥 Curtis said.
Twin and triplet births are on the decline. Here's how it breaks down by state.
Twin and triplet births are on the decline. Here's how it breaks down by state.
Twins, triplets, and other multiples have long caught the attention of "singletons," or those of us born without a built-in best friend by our sides. Twins鈥攁nd the media鈥攁nnually descend on Twinsburg, Ohio, for the ; quintuplets get a shout-out in their local paper when they ; and who could forget "Jon & Kate Plus 8," the TV show that followed every twist and turn of a family with sextuplets.
After the 1981 introduction of in vitro fertilization and other assisted reproductive technology, twin and multiple births skyrocketed in the United States. Dr. Zev Williams of the Columbia University Fertility Center told CNN have been born using IVF, or about 2% of all U.S. births, as of February 2024. In those early years of the technology, IVF procedures often resulted in the birth of multiples. That's because physicians commonly implanted several embryos with the understanding that some may not grow into fetuses.
With new and improved technology, however, fewer embryos have to be transferred during ART, resulting in fewer multiple births in recent years. While that means fewer people celebrating National Triplet Day (on March 3, of course), it also means better health outcomes for mothers and children.
partnered with to examine the decline of multiple births in the U.S. using data from the .
Michigan, Connecticut among top states with multiple births
New parents across the country find themselves caring for twins, triplets, or more鈥攚hether through IVF, other ART, or unassisted conception. However, residents in some states give birth to doubles and higher more often鈥擬ichigan, Connecticut, and Alabama lead the way in the rate of multiple births, with several Midwestern states close behind.
Several factors can increase the odds of multiple births. Families with college educations and household incomes of at least $100,000 are on IVF treatment to start or expand their families. Race and ethnicity also , as white and Asian adults are more likely to say they or someone they know has used fertility treatments, according to the Pew Research Center.
Some states mandate that health insurance companies cover at least part of families' fertility journeys (with several caveats and nuances in each law), but others actively discourage the IVF industry as it currently operates. The Alabama Supreme Court ruled in February that surplus embryos, which are routinely frozen and stored as part of the IVF process, . Therefore, if someone destroys an embryo, for wrongful death, according to CNN.
The Alabama legislature scrambled to protect the state's IVF practitioners, but the debate continues. In June, Southern Baptists, the largest Protestant denomination in the U.S., and encourage members to consider the moral and ethical questions surrounding the procedure.
As laws and public perception of ART evolve, they will continue to impact private conversations and decisions about fertility and family鈥攁s well as the rate of multiple births in the U.S.
Story editing by Mike Taylor. Additional editing by Kelly Glass. Copy editing by Paris Close. Photo selection by Ania Antecka.
originally appeared on and was produced and distributed in partnership with Stacker Studio.
Triplet and higher multiple births nosedive
In 2004, of the people younger than 35 who gave birth with the help of IVF, , and 4.9% delivered triplets, according to doctors at the Washington University School of Medicine. In 2014, 11.8% of those births were twin deliveries, and 0.4% were triplet deliveries. But there was an increase in the percentage of those undergoing IVF who had live births鈥攆rom 36.6% to 48.7%鈥攎eaning more IVF babies were born, but a larger percentage were singles instead of multiples.
This decline in multiple births resulted from technological advancements in the embryo culture media (the solution that creates an environment for the cells to grow in) and controlled ovarian stimulation, wherein a pregnant person receives medication that encourages their body to produce more eggs. With more eggs to choose from and a better environment to grow embryos, IVF patients have had more success while implanting fewer embryos in one round.
In the greater population, this has contributed heavily to a decrease in triplet and higher-order births. This is good news for moms and their babies, as births of multiples can such as premature labor, high blood pressure, and fetal growth restriction, according to the Cleveland Clinic.
The American Society for Reproductive Medicine has followed the science and recommends IVF patients limit the number of embryos they implant. Its states that most patients with a favorable prognosis should implant no more than one embryo at a time.
