Cytoplasmic transfer is an assisted reproductive technology (ART), fertility technique whereby cytoplasm from a donor egg is injected into an egg with compromised mitochondria. The resulting egg is then fertilized with sperm and implanted in a womb, usually that of the woman who provided the recipient egg and nuclear DNA.
Cytoplasmic transfer was created to aid women who experience infertility due to deficient or damaged mitochondria, contained within an egg's cytoplasm. Deficient mitochondria can lead to recurrent implantation failure, high levels of embryo fragmentation and overall poor embryo development. The incidence of compromised mitochondria increases with advanced maternal age, thought to occur near the age of thirty-five. Consequently, it has been found advantageous for young women to donate cytoplasm to older women, creating rejuvenated eggs. This is particularly desirable for couples or women who wish to genetically contribute to any resulting embryo, given cytoplasmic transfer does not interfere with the primary nuclear DNA input from the recipient egg.
Though cytoplasmic transfer does not involve the transfer of nuclear DNA, there may still be a small amount of mitochondrial DNA present from the donor. Children conceived through this process occasionally test positive for genetic material from three parents. It is therefore arguably the first example of germ line genetic modification (manipulation that affects future generations) of humans. Because of the chance for mitochondrial DNA transfer, the embryo may also be exposed to numerous diseases connected with mitochondrial DNA such as diabetes, Lou Gehrig's disease, and pervasive developmental disorders. There is much concern associated with the potential transfer of mitochondrial DNA and its unknown interaction with the foreign DNA of the recipient egg. There is also no data as to the health of maturing children conceived through cytoplasmic transfer, the first successful birth having occurred in 1997 at Saint Barnabas Medical Center in Livingston, New Jersey as a result of procedure performed by The Institute for Reproductive Medicine and Science.
Legal status 
In 2001, the Food and Drug Administration, worried about the long-term effects of creating genetic hybrids, asserted regulatory authority over cytoplasmic transfer, in effect banning the procedure in the U.S. until lengthy and extensive studies can be conducted. There is dispute as to the extent of the FDA's jurisdiction over reproductive technologies and federal law is inconclusive. The FDA claims that genetically manipulated embryos constitute a "biological product" and are therefore subject to regulation similar to medical implements and drugs. In any case, the withholding of federal funds and prohibitively expensive research costs needed to fulfill FDA regulations has resulted in movement of cytoplasmic transfer operations abroad. This has contributed to the development of reproductive tourism where infertile couples or individuals travel in order to obtain fertility treatments banned in their home country or state.
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- Cytoplasmic transfer in assisted reproduction
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