Why ‘three-parent babies’ are making the headlines


Tuesday 3rd February was a momentous day in science. It saw the initial step towards the United Kingdom being the first country to allow a revolutionary medical technique: three-parent in-vitro fertilisation (TPIVF) as it passed through the House of Commons with an overwhelming 254-vote majority.

TPIVF is a procedure that is designed to prevent the passing down of various mitochondrial diseases caused by mutations in the mitochondrial DNA (mDNA); these mutations can cause debilitating conditions such as muscle weakness, dementia and even early death, and affect 1 in every 6,500 babies born.

During the process of fertilisation, it is only the sperm’s nucleus (containing the father’s DNA) that eventually enters the egg – the rest of it is shed – and therefore all the mitochondria inherited by the child are from its mother. This means that mitochondrial mutations can only be passed down by the mother, and so it is only the mitochondria in the egg that must be altered to prevent the inheritance of disease.

TPIVF can be conducted in two slightly different ways, both ending in the same result.

Both methods consist of obtaining two eggs, one from the mother (who has faulty mDNA) and one from a donor (with functional mitochondria).

The first method (mitochondrial spindle transfer) consists of removing the nucleus of the donor’s egg and implanting the nucleus from the mother’s egg, creating an egg with healthy mitochondria and the intended mother’s DNA.

This egg is then fertilised by the father’s sperm and implanted via the traditional IVF techniques.

The second method (pronuclear transfer) involves fertilising both the mother’s egg (with the father’s sperm) and the donor egg (with any sperm); the fertilised donor egg’s nucleus is then removed and replaced with the fertilised mother’s egg’s nucleus, forming a healthy zygote that can then be implanted.

Children that will be born from this procedure have been sensationally named ‘three-parent babies’, a title obviously designed to attract the eye rather than promote scientific accuracy, yet it does contain some truth.

Since the mitochondria in the new child do contain the DNA from an individual distinct from their parents, it can be argued that the child has three genetic parents, however the amount of DNA present in mitochondria contains approximately thirty-seven genes compared to the 22,000 found within the nucleus, leading some to remark that, at most, they should be renamed ‘2.001-parent babies’.

Both methods consist of obtaining two eggs, one from the mother (who has faulty mDNA) and one from a donor (with functional mitochondria)

In addition to this, none of the genes found within the mitochondria code for any of the child’s characteristics apart from metabolism; they will look and act like their parents as much as any other child does.

As happens with many scientific breakthroughs, the concept and possibility of this treatment being put into action sparked controversy, primarily from religious groups, however all for various different reasons.

The objections range from the Catholic Church protesting pronuclear transfer due to the destruction of a fertilised nucleus to the idea of crossing ethical boundaries leading down a slippery slope to the creation of ‘designer babies’ and even the possibility that this could be classed as a form of eugenics.

However the prime concern is the lack of knowledge in this area of science as mDNA is not completely understood and so it is possible that problems could occur when the child is older or even generations down the line. Any complications that do occur will only be known once the procedure has been performed for real.

A rebuttal against this argument could be given in the form of the existence of Alana Saarinen and around forty others like her.

Alana is a ‘three-parent baby’ born in the US via a now-banned fertility treatment known as cytoplasmic transfer, a technique developed in the late 1990s which is similar to TPIVF due to the fact that cytoplasm (which contains mitochondria) was injected into the egg.

This means that Alana is alive due to a donor’s mitochondria and contains DNA from three individuals.

TPIVF has the potential to reduce the anguish and suffering of a mother burying her own child

Alana is a happy and healthy teenager, and due to other clinics performing this procedure before the ban, it is believed that around thirty to fifty ‘three-parent babies’ currently exist.

Cytoplasmic transfer did not occur without complications, with two miscarriages and one child with a possible disorder related to autism in a group of around twelve foetuses, yet it is impossible to know whether these occurred by chance or as a result of the procedure.

TPIVF has the potential to reduce the anguish and suffering of a mother burying her own child.

Through proper regulation I believe that the possible benefits outweigh the risks, and personally I will warmly welcome the new generation of so-called ‘three-parent babies’ into our world.



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