[Reading Science] "Two Moms, One Dad: The Birth of a Child with 'Three Parents'"... First Legal Birth in the UK

First Case Revealed Since Legalization in 2015
Scientists Say "Need to Confirm No Side Effects"

It has been confirmed that the world's first "legally three-parent baby" was born in the United Kingdom. This so-called "three-parent IVF" method involves extracting the nucleus from the egg of a mother with a genetic defect and implanting it into the egg of another woman who donated it, followed by in vitro fertilization with the father's sperm. It is also known as Mitochondrial Replacement Therapy (MRT).

(Photo by National Right to Life Committee (NRLC) website)

According to the international academic journal Nature on the 12th, the UK's birth regulatory authority, the Human Fertilisation and Embryology Authority (HFEA), recently responded to a related information disclosure request from the domestic media outlet The Guardian, revealing that fewer than five children had been born using this method as of April this year. This procedure was performed at the Newcastle Fertility Centre, the only medical institution in the UK authorized to carry out MRT. It is known that HFEA strictly reviews each applicant's circumstances under current law to decide whether to grant permission.

Three-parent IVF was devised to prevent genetic diseases caused by mitochondrial DNA defects. Mitochondrial DNA is maternally inherited. In other words, if the mother's mitochondrial DNA is abnormal, it is directly passed on to the child. Scientists developed a method to extract only the nucleus from the mother's egg, implant it into a normal egg from another woman, and then fertilize it with the father's sperm in vitro. This method has attracted attention because it can prevent numerous genetic diseases caused by mitochondrial DNA defects, such as muscular dystrophy. However, ethical controversies arose because it could be used to produce "designer babies." After intense debate, the UK became the first country in the world to legalize the related law in 2015. Australia also passed related legislation last year, becoming the second country to legalize it.

Many other countries still lack regulations on this matter. In 2016, an American doctor announced that he successfully performed MRT in Mexico, where three-parent IVF is not prohibited, to prevent genetic diseases caused by mitochondrial defects. Such procedures are also being carried out in countries like Greece and Ukraine. The United States has had debates but has not yet legalized it.

Scientists are paying close attention to whether there are any side effects from this procedure. Robin Lovell-Badge, a researcher at the Francis Crick Institute in London, stated, "It should be disclosed how well this three-parent IVF method has worked and whether the babies have been free from mitochondrial defect-related diseases," adding, "It is also necessary to check if there are any risks that may arise later in life, or if the women or their children are at risk of developing diseases."

There are particular concerns that a small amount of the mother's mitochondria might be transferred during the process of implanting the nucleus from the mother's egg into the donor's egg. Daegun Wells, a genetics professor at the University of Oxford in the UK, said, "I want to know to what extent mitochondria were transferred in this case and whether mitochondria containing very low levels of mutations caused any health problems." Another point of interest is how long the donor's mitochondria continue to persist over time. In animal and cell studies, a "reversal" phenomenon has been observed in some cases where the mother's mitochondria implanted into the donor's egg increased significantly over time, replacing the donor's mitochondria. Notably, Professor Wells' research team observed such a reversal phenomenon after performing MRT during infertility treatments on 25 couples in Greece. Six children were born to these 25 couples, and five of them had most of the donor's mitochondrial DNA. However, one child had between 30% and 60% of the mitochondrial DNA inherited from the mother. It is estimated that less than 1% of the mother's mitochondria were transferred to the donor's egg at the time of embryo fertilization and later expanded.

The cause of this reversal phenomenon is not yet clearly identified. However, it has been confirmed that it has no significant impact on the child's health. One suggested cause is that maternal mitochondrial DNA replicates much more easily than the mitochondria included in the donor's egg or embryo. In this case, matching egg donors and recipients with mitochondrial DNA as similar as possible can reduce replication ability. Differences in fertilization methods are also noteworthy. Among the five children who retained the donor's mitochondrial DNA, the mother's eggs were frozen and thawed before implantation. In contrast, the child who experienced the reversal phenomenon had both the donor's and recipient's eggs in a fresh, unfrozen state.

Furthermore, the news of the UK's first-ever legally born three-parent IVF baby is also seen as an opportunity to establish procedures for careful national-level approaches and management regarding such ethical and medical issues.