If a woman has mitochondrial disease, there is a risk that when she tries to conceive naturally the disease may be passed onto her child. This is because mitochondrial DNA is inherited from the mother.
People in this situation have a number of options available to reduce the chance of this happening. However, there are advantages and disadvantages associated with each option.
Current available options to avoid mitochondrial disease include:
A woman, or couple, may choose to adopt a child rather than conceiving naturally. This will mean that they do not risk passing on mitochondrial disease to their child. However, the child will not be genetically related to either of the intended adoptive parents.
In vitro fertilisation (IVF) is a process in which an egg is surgically removed from a woman’s ovaries and fertilised with her partner’s sperm outside the body. The subsequent embryo is later placed in the woman’s womb.
People affected by mitochondrial disease may choose to have a child through IVF with eggs donated by a woman who does not have mitochondrial disease. However, the child will not be genetically related to the intended mother.
An alternative to IVF with egg donation or to adoption is to create embryos using IVF and then test them to see if mitochondrial disease is present.
Any embryos without the disease would then be transferred to the intended mother. This technique is called preimplantation genetic diagnosis (PGD).
PGD gives people the opportunity to reduce the chance of having a child with mitochondrial disease. However, it cannot guarantee a child free from disease. This is because an egg can either contain mitochondria that are all unhealthy, or it can contain some healthy and some unhealthy mitochondria.
When choosing an embryo using PGD, embryos with the lowest number of unhealthy mitochondria can be chosen, which reduces the chance of having an affected child. However, there is still a chance of the disease developing.
Another option is to have a child naturally, and then to test the fetus during the pregnancy to find out whether the child will be born with a particular disease. This technique is called prenatal diagnosis (PND).
If a fetus is diagnosed with mitochondrial disease, the prospective parents could decide to continue the pregnancy or could opt for a termination of the pregnancy. Parents could be offered IVF with PGD (pre-implantation genetic diagnosis) followed up by PND to confirm if the child will be born free of the disease. As with PGD, it cannot guarantee that the baby born will be unaffected. Even if a girl is born and appears healthy, she may herself carry a proportion of unhealthy mitochondria, which could lead to her children being affected by mitochondrial disease.
UK researchers are developing medical techniques that could allow mothers to avoid passing on genetically inherited mitochondrial diseases to their children. The techniques, maternal spindle transfer (MST) and pro-nuclear transfer (PNT) involve a degree of genetic modification. While these techniques, if successful, could save lives, they also raise ethical questions.
Find out about these techniques and the ethical issues they raise: