If the experiment is successful, the treatment could cure foetuses scheduled for abortion because of a potentially fatal genetic disorder - creating an unprecedented ethical dilemma.
The idea, proposed by Dr French Anderson of the University of Southern California in Los Angeles, would try to replace faulty genes in two diseases: those which cause the inherited blood disease alpha-thalassaemia, and those which lead to "severe combined immune deficiency.
Dr Anderson admitted that if his experiments succeeded, then the aborted foetus might survive and thus remove the reason the parents wanted an abortion in the first place.
"The parents and researchers will have this guilt that I'm not sure it's possible to emotionally prepare for," he told New Scientist magazine.
Gene therapy aims to alter an individual's DNA - the blueprint for the body - and replace faulty genes with working copies in body cells.
Millions of pounds have been spent in the past few years around the world on hundreds of experiments, but none has so far cured any patients.
Women whose babies have inherited the faulty genes that lead to alpha- thalassaemia often develop the potentially fatal condition called pre- eclampsia, which can kill the mother in a matter of hours.
When alpha-thalassaemia is detected by genetic tests, many will choose to abort the foetus. Dr Anderson intends to ask women who have made that decision to let him try gene therapy to correct it.
Dr Anderson made the proposal last month to a panel at the National Institutes of Health.
But one panelist, Louise Markert, an immunologist, said: "Is it morally right to experiment on the foetus when it can give no consent and there is no way for it to benefit from the therapy?"
Dr Anderson said he would not be ready to carry out the experiments for at least three years.Reuse content