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Three-parent babies

Sophie Carr talks us through the science behind the three-parent baby, and its social implications


This year the UK is expecting the arrival of its first three-parent babies. We’re not sure exactly when these babies will be born, but we know that last year the Human Fertilisation and Embryo Authority approved two cases for the go-ahead at a fertility clinic in Newcastle.

Obviously the first question to answer is how can a baby have three parents?

The process of creating these babies is called mitochondrial replacement therapy and is being performed to prevent children from inheriting mitochondrial disorders. Mitochondria are found in almost all of our cells and work to provide the cells with energy. When these mitochondria aren’t working properly people suffer from severe illnesses, such as Leigh syndrome, a neurological disorder that often prevents children from surviving past infancy. These mitochondrial disorders can occur spontaneously via random mutations in someone’s DNA or can be inherited from mothers who suffer from such diseases. It’s thought that around 3000 women in the UK are affected by mitochondrial disorders, and mitochondrial replacement therapy could potentially help these women if they wish to mother healthy children.

This technique has already successfully conceived children in New York and Ukraine, and now the UK has officially approved the use of mitochondrial replacement therapy and can begin using the treatment.

Many people are against the whole idea, claiming that this process is a slippery slope towards unethical practices

The process works similarly to IVF. If a mother who suffers from a mitochondrial disorder wants a baby, her eggs would be harvested and the nucleus (which contains most of her DNA) is removed. This nucleus can be inserted into a donor egg (which has had its nucleus removed) containing healthy mitochondria. Then the egg would be fertilised with a male’s sperm and implanted into the mother or a surrogate.

A tiny amount of DNA is present in mitochondria, 37 genes to be exact, meaning that 37 genes that the baby will inherit come from the healthy egg donor. These genes supposedly don’t influence the child’s appearance or personality but do mean that the egg donor is biologically related to the child in addition to the mother who’s nucleus was implanted into the egg. Therefore the baby inherits DNA from a mother, a father and tiny proportion from a donor.

Mitochindrial DNA. Source: wiki commons

As you can imagine, there are many social implications from the possibility of three-parent babies.

Firstly, as the child will inherit genes from two mothers, lesbian couples who want a baby now have the opportunity to both biologically mother a child. More than this, the door has potentially been opened to those in open relationships, three-way relationships or even just groups of three committed friends to biologically conceive a child. However these are undoubtedly far-fetched ideas at present, as currently the UK has only approved the use of mitochondrial replacement therapy for preventing mitochondrial disorders and there are no indications that the procedure is being considered for non-disease-preventing reasons.

Legality issues could also be raised from the child having three parents. Current practice is that the egg is donated from an anonymous donor, but what if this changes in the future so that the donor could be involved in the child’s life? If problems arose, who would get custody of the child? Who would be ultimately responsible for making decisions for the child? There are lots of potential questions without answers.

lesbian couples who want a baby now have the opportunity to both biologically mother a child

Many people are against the whole idea, claiming that this process is a slippery slope towards unethical practices such as genetically engineering babies to have certain features. In a way, that is exactly what the procedure intends to do, but with the non-maleficent intention to prevent children from suffering. However some believe that mitochondrial replacement therapy is a form of eugenics that should not be accepted into society.

The scary issue is that the outcomes of the process are pretty much unknown. What if the procedure fails to actually prevent the disorders it’s trying to avoid? Some studies have shown that in about 1 in 20 cases the child could still inherit a mitochondrial disorder, as a few mitochondria are still transferred alongside the mother’s nucleus into the donor egg. This would undoubtedly be a disaster after the lengthy and expensive process involved in trying to avoid this.

Whether people agree with three-parents babies or not, it’s happening right now in the UK and we will soon find out what degree of success it will bring.


For more on the social implications of genetic engineering, check out this article by Alina Ivan on Designer Genes

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