"Thousands of women could benefit from 'three-parent' baby technique," The Independent reports. A modelling study estimated the technique, which is currently illegal, could be used for thousands of women with genes linked…
"Thousands of women could benefit from 'three-parent' baby technique," The Independent reports. A modelling study estimated the technique, which is currently illegal, could be used for thousands of women with genes linked to serious mitochondrial DNA diseases.
The news is especially topical as it was announced today that parliament is set to vote in February about whether to make the technique legal.
"Three-parent" IVF is designed to prevent babies being born with mitochondrial conditions. Mitochondria are the "powerhouses" within our cells that convert sugar into energy.
A baby inherits its mitochondria from its mother, and women with mutations in their mitochondrial DNA are at risk of passing on a mitochondrial genetic disorder to their offspring.
Mutations in mitochondrial DNA can cause a range of disorders affecting the muscles, heart, brain and eyes. Some children can be severely affected and have a reduced life expectancy. There is currently no cure.
The new techniques use healthy mitochondria from a donor egg to replace the mitochondria in the mother's egg, either before fertilisation or just after, to prevent passing on mutations.
While on a technical level a baby conceived in this way would have three "parents", in practice only 1% of genetic information would come from the third "parent" (the egg donor).
The modelling study attempted to estimate the number of women in the UK and US who could benefit from such techniques. This aims to help inform decisions around whether the technique should be allowed.
The study estimated 2,473 women in the UK could benefit from the new IVF technique. This was based on the proportion of women known to be at risk in the north east of England, so does not take into account variations across the UK or US in terms of ethnic diversity or average maternal age.
As this technique is untried, it is currently unknown how effective it may be, or what the short- or long-term consequences are.
Where did the story come from?
The study was carried out by researchers from Newcastle University.
It was funded by the Wellcome Trust Centre for Mitochondrial Research, the Newcastle University Centre for Ageing and Vitality, the Medical Research Council, the Lily Foundation, the UK National Institute for Health Research, and the UK NHS Specialist Commissioners Rare Mitochondrial Disorders of Adults and Children Service.
The study was published as a letter in the peer-reviewed New England Journal of Medicine on an open-access basis, so it is free to read online.
The UK media reporting was accurate, though it wasn't pointed out we still do not know how effective or safe the techniques might be.
What kind of research was this?
This study aimed to estimate how many women in the UK and US might benefit from new IVF techniques that use donor mitochondria (sometimes referred to as "three-parent" IVF). These techniques aim to prevent women passing mitochondrial mutations on to their offspring.
The researchers based these estimations on data on how many women have a mitochondrial DNA (mtDNA) mutation and whether this affects their fertility.
As these techniques are not currently legal, before they can be used they require new regulations to be passed in parliament regarding the Human Fertilisation and Embryology Act (1990).
In simple terms, the new techniques involve either:
- taking the DNA from the nucleus of the egg that has just been fertilised (most of our DNA is found in the nucleus) and transferring it to a donor egg that has had the nuclear DNA removed, but still has the healthy mitochondria and mtDNA
- taking the mother's DNA from the nucleus of her egg and inserting it into a donor egg that has had its nuclear DNA removed, but still has healthy mtDNA intact – fertilisation would then take place using the donor egg and father's sperm
Behind the Headlines discussed these techniques in more detail back in June 2014.
These techniques are controversial – at present, it is against the law to modify DNA before or after fertilisation because of concerns about the ethics of changing people's DNA in a way that will be inherited in generations to come.
Indeed, no country in the world has passed regulations for these techniques to be used. Because of this, it is important that the health, social, ethical and legal implications are considered fully before any decisions are made.
Still, it is worth considering that similar concerns were raised when IVF was first introduced in the late 1970s, and it is now considered standard practice.
As this technique looks like a promising way to avoid certain diseases, the Department of Health put out a public consultation in February 2014 on whether these techniques should be allowed to be used. Following the responses received, parliament is set to vote on the issue in February 2015.
What did the research involve?
The number of women in the UK and US who have the potential to pass on an mtDNA mutation was first estimated. This was based on the percentage of women of childbearing age who have been identified in the north east of England as having mtDNA mutations, as well as their fertility rate.
The researchers used data from the UK Office for National Statistics to calculate fertility rate in the general population. They then compared this with data on women who are carriers of a disease-causing mtDNA mutation from the MRC Mitochondrial Disease Cohort UK to see if fertility is affected by these mutations.
They also had local data from the north east of England on the proportion of women who had an mtDNA mutation. They used these figures to estimate the likely number of women affected in the rest of the UK and US.
What were the basic results?
Fertility rates were not reduced in women with a disease-causing mtDNA mutation. The researchers identified 154 women with such mutations from the MRC Mitochondrial Disease Cohort, and found their fertility rate was 63.2 live births per 1,000 person-years, compared with 67.2 in the general population.
They say that in women most severely affected, the rate was 50.6 live births per 1,000, compared with a similar group of women in the general population with a rate of 52.6 live births per 1,000.
Based on this, the estimated number of childbearing-age women at risk of passing on a mitochondrial disease was:
- 2,473 women in the UK
- 12,423 women in the US
How did the researchers interpret the results?
The researchers concluded if all women in the UK estimated to have an mtDNA mutation wanted to have a child and had the new IVF procedure, this could benefit 150 births per year.
This study has provided an estimate of the number of women of childbearing age who might pass on an mtDNA mutation to their offspring. The researchers say this is nearly 2,500 women in the UK and could affect 150 births per year.
However, as the authors point out, the estimates do not take into account the following factors, which vary across the UK and US, compared with the north east of England:
- average age of women giving birth
- ethnic diversity
- actual number of women with a mitochondrial DNA mutation
The researchers also acknowledged that even if the new regulations are passed, not all women would necessarily have access to the new IVF technique, or would want it.
As these new IVF techniques are not currently legal, they have not resulted in the birth of any babies conceived using them. It is therefore not known how effective the techniques might be, or what the short- or long-term consequences are.
The Department of Health put out a public consultation on whether these two techniques should be allowed to be used in February 2014. Following the responses, parliament is set to vote on the issue in February this year.
It is difficult to predict the outcome of the vote. At the time of writing, there has been no official party whip announced by the various political parties on how their MPs should vote.
Most commentators expect it to be a free vote, where MPs are left to vote according to their own personal beliefs, which makes it even harder to predict.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.