Mom and dad and mom know best: three-parent babies are now possible. Congress should get out of the way.

• Author: Bailey, Ronald
• Position: Columns - Mitochondria replacement therapy

CURING SICK BABIES shouldn't be controversial. But when it comes to limiting parental rights to use all the tools at their disposal to have healthy kids, old-fashioned doctor-knows-best paternalism is quickly being replaced by bioethicist-knows-best paternalism--or worse, by panel-of-bioethicists-knows-best paternalism. That is what's happening with a promising new set of treatments called mitochondria replacement therapy (MRT).

Every cell has scores of mitochondria swimming in its cytoplasm, providing the energy that keeps the cell functioning. Human mitochondria have their own sets of 37 genes located outside the cellular nuclei. Because egg cells, but not sperm cells, contribute mitochondria to developing embryos, children can only inherit their mitochondria from their mothers.

As with other genes, sometimes mitochondrial genes mutate and cause disease. As many as 1 in 200 Americans carries a mitochondrial DNA mutation that could lead to disease, and researchers have identified more than 250 pathogenic mitochondrial DNA mutations so far. One such disease is Leber hereditary optic neuropathy, which afflicts perhaps 1 in 15,000 people and is characterized by vision loss beginning in patients' teens and 20s. Another is mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes, the prevalence of which is 1 in 5,000 people. Sufferers experience the onset of strokes and dementia generally before age 40. Somewhere between 1,000 and 4,000 children are born every year in the U.S. suffering from some kind of mitochondrial disease.

Researchers hit on the idea of curing such diseases by replacing defective mitochondria with healthy ones derived from eggs donated by other women. Back in 2001, fertility specialist Jacques Cohen and his colleagues at St. Barnabas Hospital in New Jersey transferred ooplasm containing mitochondria from healthy donor eggs to the eggs of women experiencing infertility. The treatments resulted in the births of 17 babies. Sixteen are healthy; one was later diagnosed with autism. What role the ooplasm transfer may have played in that case, if any, is unknown.

Cohen's work was opposed by the usual bioethical busybodies. As The New York Times reported in 2001, "Two ethicists, Erik Parens of the Hastings Center in Garrison, N.Y., and Eric Juengst of Case Western Reserve University in Cleveland, suggested that such treatments, because they result in permanent genetic alterations that in turn will be passed on to...