Ooplasmic transfer, also known as cytoplasmic transfer, is an experimental fertility technique that involves injecting a small amount of ooplasm from eggs of fertile women into eggs of women whose fertility is compromised. The modified egg is then fertilized with sperm and implanted in the uterus of the woman attempting to achieve pregnancy.

Children born from this procedure have been reported to possess cytoplasmic organelles called mitochondria from both their biological mother and the ooplasmic donor, a condition referred to as mitochondrial heteroplasmy. Because mitochondria carry their own sets of genes that are passed on to succeeding generations, the mixing of parent and cytoplasmic donor mitochondria might be considered to be a form of germline modification. However, the technique does not involve modification of particular genes and could not be used as part of any procedure to create "designer babies."

In 2001, researchers at St. Barnabas Hospital in New Jersey announced that they had used ooplasmic transfer to enable several women with impaired fertility to bear children. They described their work to the press as "the first case of human germline modification."

However, ooplasmic transfer is not germline genetic modification, or inheritable genetic modification (IGM), in the usual sense. It cannot be used to modify genes housed in the cell nucleus, which influence all traits except for those regulated by mitochondrial genes. But the procedure might be considered a form of IGM in that the mixed mitochondrial DNA would be passed on to all future generations.

On the other hand, some advocates of IGM have identified ooplasmic transfer as a technology whose development and use could be used to help erode popular resistance to IGM. 

Following the St. Barnabas announcement, the FDA notified all US fertility clinics known to be offering the procedure that further ooplasm transfer protocols could not proceed without FDA approval.

On May 9, 2002, an FDA Advisory Committee held a public meeting to discuss ooplasm transfer procedures. A statement issued by the FDA at this meeting reported that at least two dozen births attributed to ooplasm transfer have been reported by three fertility clinics since 1998.

The FDA expressed concerns about this "de facto germ line gene transfer" technique, citing its potential to alter the germline, the medical risks associated with mitochondrial heteroplasmy, the high incidence of Turner's syndrome in fetuses reported in one study (2 of 13 reported pregnancies), and the paucity of animal studies and other pre-clinical data. A general consensus was reached at the meeting that more preclinical data would be necessary before FDA would allow further clinical trials involving ooplasm transfer to proceed.