Early last fall, the world celebrated the birth of a very special baby. For the first time in history, a child was born who had the DNA of three parents, according to New Scientist. The fertility doctor behind this groundbreaking science is John Zhang—along with his team at New York’s New Hope Fertility Center. 
For women with rare genetic mutations that are passed on to their babies, this technique of using the DNA from three parents could be the breakthrough that makes it possible for them to give birth to healthy children. This very first baby was born to a family from Jordan (the family has not shared their names publicly). The mother has a genetic mutation called Leigh syndrome that is fatal to developing children. 
The couple had lost four pregnancies and two children to complications related to this mutation, so they were up for trying a more unconventional approach. After nearly two decades of infertility, the couple reached out to fertility specialist Dr. Zhang.
The Science Behind the Three-Parent Baby
We’re sure you’re curious about how Zhang and his team pulled off this impressive accomplishment. We had questions, too! We did some digging to uncover the science behind the three-parent baby, and it’s nothing short of fascinating. 
Leigh syndrome is a disorder of the mitochondria. In this mother’s case, 25 percent of her mitochondria had a mutation that was causing her disease. Although she exhibited no symptoms, this mutation is passed from mothers to their children. For this mother, this meant the heartbreak of four miscarriages and the death of the two children she was able to carry—one at the age of 6 and the other at 8 months of age. 
Mothers like this are exactly the people fertility specialists like Zhang and his team hope to help with their experimental techniques. In this case, a procedure called spindle nuclear transfer was used to target the problem with her mitochondria. Using a type of gene replacement therapy, they performed a spindle transfer on oocytes of one woman to the oocytes of the mother with Leigh syndrome. This technique has gotten more attention recently as an option for preventing the transmission of mitochondrial mutations from mother to baby. 
After the spindle transfer, the oocyte was then fertilized with the father’s sperm, and the mother underwent in vitro fertilization using this new, three-parent egg. Although teams of researchers have performed a spindle transfer in the past on unfertilized eggs, this is the first time a family has fertilized and brought a three-parent baby to term.
The Ethics of the Technique
One of the most fascinating aspects about this story is the extreme measures that were taken to honor the wishes the couple had to remain faithful to their religious convictions as Muslims. 
In fact, the method used was not the only available option for the couple. They also could have chosen to fertilize two embryos, both the mother’s and the donor’s. After fertilization, the nucleus of the mother’s egg would have replaced the nucleus of the donor’s egg. 
Because this required discarding the nucleus of the fertilized donor egg, the couple chose what they felt was the more ethical of the two options. Additionally, they made the decision to choose the sex of their baby to be a boy. Their hope in doing so was to break the cycle of passing down Leigh syndrome, which is inherited from the mother. 
Even so, techniques such as the one used still remain controversial, especially to some pro-life organizations that have criticized this technique as extreme and risky. Because of the questions that remain concerning the ethics of a three-parent pregnancy, the New York–based clinic performed the procedure in Mexico, where no regulations exist for this type of in vitro fertilization, according to New Scientist.
Life as a Child of Three Parents
The baby was born in April 2016 and has experienced healthy development so far. After testing the little boy’s mitochondria, Zhang and his team found that only 1 percent of it carried his mother’s mutation. 
Current evidence indicates that at least 18 percent of the mitochondria must carry the mutation to be harmful to the child. This seems to suggest that the three-parent child has a high chance of growing up to live a healthy life. Just days before the baby celebrated his first birthday, Zhang and his team gave an update. At their last check-in with the family, the boy was 7 months old and showing no symptoms that indicate the mitochondrial mutation is negatively affecting his health. 
At this time, the family has chosen to only monitor his symptoms, opting out of any further genetic testing unless clinically necessary. Practically speaking, life as a child of three parents won’t look much different for him than that of a two-parent child. Although this child is biologically the child of three, typical egg donation protocols were followed. 
This means the donor’s identity was kept anonymous, and the recipient couple was not in contact with the donor in any way. It doesn’t look like there are any chances of creative co-parenting agreements being made, so this baby will be raised by his mother and father—and the donor may never know her eggs were used for such a remarkable procedure.
What’s next for three-parent babies?
Since the birth of the first three-parent baby, the world of infertility treatment has reached another major milestone. In January 2017, the first three-parent baby girl was born to a family in Ukraine, according to CNN. 
This specific birth was controversial, because countries such as the U.K. have only approved the use of this technique if the mother has a mitochondrial mutation. In the case of the Ukrainian couple, the mother did not have such a mutation; instead it was reported they were experiencing infertility with an unknown cause. Another controversial aspect of this case was the fact that the baby was a girl, which brought up concerns that she may carry a mutation that could be passed to her own children. 
But the couple’s medical team completed extensive testing before the decision was made to move forward with in vitro fertilization after the team discovered that no male embryo had developed. It’s hard to say for sure what the future holds for three-parent babies. According to Zhang, the next step is simple: to continue to monitor the children born using this approach and to move forward with scientific study until further conclusions can be made concerning the safety and effectiveness of using three parents as a solution for mothers with mitochondrial mutations who are experiencing infertility. 
After that, there seem to be big dreams for the future of infertility treatment, as Zhang has said he hopes to commercialize this method of infertility treatment, making it possible for older mothers experiencing infertility to conceive healthy children using the spindle nuclear transfer technique.
