The miracle of science and medicine: The case of the three-parent child

Chelsea Maniscalco
Contributing writer for Baby Sleep News

After having several miscarriages and two deceased young children, one woman was ready to try anything to have a healthy child. Surprisingly, this 36-year-old woman and her partner did not have any symptoms of a disease that would lead to an explanation. The reason was uncovered by science – she has bad mitochondria. Mitochondria are the major source of energy for cells. The mitochondria disease this mother has, called Leigh syndrome, is only passed on from mother to child. This is termed a maternally inherited disease, and this was causing her children to have a short life.

Current clinical possibilities to prevent this transfer of bad mitochondria from mother to child are few in number. Some options are: 1) The parents could adopt a child, 2) they could use a donor egg and avoid using the mother’s egg with bad mitochondria, or 3) they could get pregnant and do pre-natal testing to determine if the baby will have the disease and possibly abort an affected pregnancy. The first two options prevent you from having a child with your genes, and the last option would be very difficult to experience.

An alternative option, which faces opposition due to ethical reasons, was presented to this mother. Their child could still be genetically their own, but they would use good mitochondria from a donor egg. The idea would be to still use the mother’s DNA, which is in the nucleus of her egg, and the father’s DNA, which is in his sperm. Dr. John Zhang and his colleagues removed the nucleus from the mother’s egg, which left behind most of the bad mitochondria, and placed it into a healthy donor’s egg that had the nucleus removed. So now this egg had the genetic content from the mother, but the good mitochondria from the donor egg. (See cartoon.) This egg was then fertilized by the father’s sperm and implanted into the mother to grow and develop into a baby.

This procedure of removing the mother’s nucleus and relocating it into a donor egg, called spindle transfer, was approved and performed in Mexico (this procedure has not been approved in the United States). The mother was prepped at a fertility clinic in New York and then flew to Mexico to have the actual procedure performed.

At 37-weeks of gestation, a healthy baby boy was born! From news articles to scientific publications, this procedure has been widely publicized. Check out the editorial and the NPR article to read more on the implications of this treatment.

Scientists anticipate that this boy will not have any of the symptoms associated with Leigh syndrome. His mitochondria was tested to ensure that he is healthy. People show severe symptoms with approximately 60-70% bad mitochondria. His mother has approximately 27% bad mitochondria, which is why she does not display any symptoms. The baby has approximately 6% bad mitochondria, so the procedure worked, dramatically reducing the amount of bad mitochondria transferred to him from his mother. Importantly, since this mitochondrial disease is passed from mother to child, there is no risk that he might pass this disease on to his children. As of April 2017, the boy was a healthy 7-month-old child. He will be regularly checked throughout his life, but this technique is expected to give him that long life his parents so desired for their child.