Three-parent babies are human offspring with three genetic parents, created through a specialized form of In vitro fertilisation in which the future baby's mitochondrial DNA comes from a third party. The procedure is intended to prevent mitochondrial diseases including muscular dystrophy and some heart and liver conditions. It is the subject of considerable controversy in the field of bioethics.
Alana Saarinen is a 13-year-old girl from the US who has DNA from three biological parents. She is the daughter of Sharon and Paul Saarinen, and a third donor. Before her birth, her parents had gone through four attempts to have a baby through numerous IVF procedures without success. Unlike other attempts, Alana was a fifth succeeded attempt through an infertility treatment, known as cytoplasmic transfer. The treatment involved with the transfer of a third donor's cytoplasm, containing healthy mitochondria, to Sharon Saarinen's egg with unhealthy mitochondria. The egg was then fertilized with Paul Saarinen's sperm. During the process of transferring DNA, some DNA from the donor was in the embryo. Ninety-nine percent of Alana's genetic material is from her parents, and her one percent is from the third donor 
According to Sharon Saarinen, Alana's mother, Alana is healthy and has a fairly normal life as a teenager such as playing golf and the piano, listening to music and hanging out with friends. Despite the success of Alana's case, cytoplasmic transfer technique was banned by the Food and Drug Administration in 2001 due to safety and ethical concerns. As the result of the pioneering infertility treatment, several research teams in the United Kingdom are currently requesting a regulatory approval for a similar technique called mitochondrial replacement. The technique would use a donor's healthy mitochondria to treat women at risk of passing on mitochondrial diseases to their children
The process, still in the research stage, is currently prohibited in the United States, but is being actively researched in China. Some research is also taking place in the United States and in the United Kingdom where the government said they were planning to make the procedure legal in 2014.
The process of producing a three-parent baby, Three Parent In Vitro Fertilization (TPIVF), involves taking the nucleus of one egg and inserting it into the cytoplasm of another egg which has had its nucleus removed, but still contains mitochondrial DNA, and then fertilizing the hybrid egg with a sperm. The purpose of the procedure is to remove a nucleus from a cell with defective mitochondria and place it in a donor cell with healthy mitochondria, which after fertilization will contain a nucleus with genetic material from only the two parents. There is more than one method of TPIVF. The two main methods are pronuclear transfer and spindle transfer; Spindle transfer is a process where the spindle of chromosomes taken from the mother’s egg are placed into the donor egg and pronuclear transfer is the process described at the beginning of this paragraph.
Although the donor egg is said to contribute only 0.1% to the genetic make up of the child, when examining the genetic material of these children there are still three identifiable genetic parents. This is due to the fact that the donor egg came from a non-maternal relative. For the child to have only two identifiable genetic parents and still have undergone this procedure, the donor egg must have come from a maternal relative because maternal mtDNA is almost identical. Maternal relative egg donation is not commonly used, because if the female egg has a mitochondrial disease then it is highly likely that the maternal relatives inherited the disease as well.
Despite the promising outcomes of the two techniques, pronuclear transfer and spindle transfer, mitochondrial gene replacement raises ethical and social concerns. According to Darnovsky, an executive director of the Center for Genetics and Society, the technique procedures would involve modification of the germline, and modifications would pass on to subsequent generations. Using Human embryos in vitro research are controversial because embryos are created specifically for research and the financial compensation of egg donors. Implications for identity is another ethical concern that has psychological and emotional impacts on a child's life regarding of a person's sense of identity. It debates whether the genetic make-up of children born as a result of mitochondrial replacement affect their emotional well-being when they are aware that they are different from other healthy children conceived from two parents. Safety and efficacy of mitochondrial DNA replacement are still unanswered.
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New York University researcher James Grifo, a critic of the American ban, has argued that society "would never have made the advances in treating infertility that we have if these bans had been imposed 10 years" earlier.
Opponents argue that scientists are "playing God" and that children with three genetic parents may suffer both psychological and physical damage. These critics include Alison Cook of Great Britain's Human Fertilization and Embryology Authority, who argues that bans were "written to protect the welfare of the embryo and the child."
- Three-parent IVF needs more research, review says - BBC News article
- Short film with experts discussing the ethical / practical issues surrounding 'Three Parent Babies' / 'Mitochondria Replacement'
- Why We Should Approve 'Three-Parent' Embryos - Real Clear Science Article
- In depth: three-person IVF is about saving lives, not a slippery slope to eugenics - Wired Article
- 'Three-parent babies' cure for illness raises ethical fear - The Guardian Article
- Three-parent babies on the way, say IVF experts - The Independent Article
- 'Three-Parent' IVF Technique Set for Approval - Web MD Article
- Proposed IVF Technique Uses Three Parents - The ABC News Article
- THREE-PARENT IVF IS HERE, AND THERE’S NOTHING TO FEAR - An Al Jazeera Article
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- Now, a three-parent baby
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- Amato, P., Tachibana, M., Sparman, M., & Mitalipov, S. (2014). Three-parent in vitro fertilization: Gene replacement for the prevention of inherited mitochondrial diseases. Fertility and Sterility, 101(1), 31-35.
- Check E (November 2005). "Gene study raises fears for three-parent babies". Nature 438 (7064): 12. doi:10.1038/438012a. PMID 16267521.