An elite panel of scientists and bioethicists Wednesday offered guarded approval of a novel form of genetic engineering that could prevent congenital diseases but would result in babies with genetic material from three parents.

The panel, which was convened last year at the request of the U.S. Food and Drug Administration, said that it is ethically permissible to “go forward, but with caution” with mitochondrial replacement techniques, or MRT.

The new clinical procedures should be used rarely, with extreme care and abundant government oversight, and initially applied only to male embryos, concluded the committee, which delivered its findings at the National Academy of Sciences in Washington.

The new report comes at a time of dazzling advances in genetic engineering and a commensurate struggle to understand the ethics of “playing God,” a phrase invoked twice Wednesday by committee member R. Alta Charo, a professor of law and bioethics at the University of Wisconsin.

The FDA last year asked the Institute of Medicine to review the ethical implications of this genetic engineering, which would result in what has been loosely referred to as “three parent babies.” British officials have already approved investigatory experiments involving the technique.

Certain serious congenital diseases can be passed from a mother to child via the tiny amount of genetic material contained in the mitochondria, which are small organs within a cell that are often described as the cell's energy factories. New experimental techniques involving in vitro fertilization make it possible to replace mutated and potentially disease-associated mitochondrial DNA, or mtDNA, with nonpathogenic mtDNA donated from another woman. MtDNA contains 37 genes and is distinct from nuclear DNA, or nDNA, which has upward of 20,000 genes in humans. MtDNA is only found in eggs and thus is passed only from mother to child. That's why the panel recommended limiting the experimental procedures at first to male embryos.

The males-only guideline is intended to prevent the introduction of unwanted, irreversible genetic changes to the human species. Any genetic changes associated with this kind of engineering will meet a dead end in males.

“If there are adverse events, they would not be reverberating down the generations,” Charo said.

The procedure should be extended to females only after the long-term effects are better understood, the committee concluded.