Not only would stem cells taken from a consenting adult be ethically acceptable to most people and governments, they would also be better for patients. Imagine you had a disease killing your brain cells. Stem cells could be taken from your bone marrow, manipulated in the laboratory so that they become brain cells, and implanted back into your brain - hence no rejection of the transplant by your immune system.
This is a fantastically exciting prospect - if it works. Early results look promising, but scientists don't know how versatile stem cells from bone marrow really are. They are far more confident of what stem cells from embryos can do.
Ultimately, different stem cell types might best treat different diseases, so most scientists would opt for continued research on both types.
A final option for a source of stem cells is umbilical cord blood - usually discarded at birth. For some time now, mothers have been able to donate the stem cells within their babys umbilical cord to public cord blood banks. Cord blood collected in this way has been used to successfully treat leukaemia and immune disorders in unrelated patients. Now companies have begun offering a service to collect and store a mothers placental blood for a fee. This blood could be used to treat the baby if it were ever ill.
The companies claim that in the future, cord blood could provide a source of stem cells to cure stroke, heart disease, diabetes, Parkinson's disease and Muscular Dystrophy. In addition, at the moment these stem cells could be used to treat blood disorders such as leukaemia.
This procedure raises issues such as, perhaps only the rich will be able to store their cells, and that in some disorders the cord stem cells will also be affected and therefore no good to transplant.
The beauty of collecting these stem cells is that they are taken without affecting the mother or child. They are also 100% compatible with the baby should he or she ever develop an illness and be in need of stem cells.
These companies argue that in addition, the cord blood from the baby might provide a source of compatible stem cells for the baby's relations - brothers and sisters, parents and grandparents.
For a few thousand dollars - could you afford not to store them?