In August 1996, at St. Barnabas Medical Center in Livingston, N.J., a 39-year-old mechanical engineer from Pittsburgh named Maureen Ott became pregnant. Ott had been trying for almost seven years to conceive a child through in vitro fertilization. Unwilling to give up, she submitted to an experimental procedure in which doctors extracted her eggs, slid a needle through their shiny coat and injected not only her husband’s sperm but also a small amount of cytoplasm from another woman’s egg. When the embryo was implanted in Ott’s womb, she became the first woman on record to be successfully impregnated using this procedure, which some say is the root of an exciting medical advance and others say is the beginning of the end of the human species.
The fresh cytoplasm that entered Ott’s eggs (researchers thought it might help promote proper fertilization and development) contained mitochondria: bean-shaped organelles that power our cells like batteries. But mitochondria also contain their own DNA, which meant that her child could possess the genetic material of three people. In fact, the 37 genes in mitochondrial DNA pass directly from a woman’s egg into every cell of her offspring, including his or her germ cells, the sperm or eggs that eventually produce the next generation — so if Ott had a girl and the donor mitochondria injected into Ott’s egg made it into the eggs of her daughter, they could be passed along to her children. This is known as crossing the germ line, something that scientists generally agree is a risky proposition.
Ott, who is Catholic, remembers weighing whether altering the makeup of her descendants in this way was O.K. “Being a person who’s been involved in science my whole life, the way I looked at it is: God gives us doctors to help us, and they help us with things like infertility,” she told me recently. As far as anyone knows, mitochondrial DNA (mtDNA) governs only basic cellular functions; Ott understood that her and her husband’s nuclear DNA would determine their child’s characteristics — height, eye color, intelligence and so on. “If I was doing something like, say, I only wanted a blond-haired girl, I would feel that was unethical,” she said. “But what I was trying to do was use whatever medical procedures were available to me to get pregnant, and I didn’t think that was unethical.” In May 1997, she gave birth to a healthy baby girl.
Two months later, her doctors published her case in the journal Lancet; soon, at least seven other U.S. clinics were doing the injection. Because the amount of donor mitochondria added to Ott’s egg was small, it was unclear how much third-party DNA would be present in the cells of her daughter. Ott says her doctors ran tests and did not find any, but it has been found in two other children born from the procedure. Although I.V.F. drugs and devices are regulated by the Food and Drug Administration, I.V.F. procedures (like all medical procedures) are generally not. But what media outlets came to call “three-parent babies” compelled the agency to take action. In 2001, the F.D.A. informed I.V.F. clinics that using a third person’s cytoplasm — and the mtDNA therein — would require an Investigational New Drug application.