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Yet another fertility-boosting procedure sounds almost as if it came from science fiction. Researchers know that older women's eggs are less fertile than those of younger women, and suspect that the fault lies not in the chromosomes but in the biological machinery that controls cell division. To test this idea, Dr. Jamie Grifo, director of reproductive endocrinology at New York University Medical Center, and his colleague, Dr. John Zhang, have microsurgically transplanted the chromosome-containing nuclei from older women's eggs into younger women's eggs from which the nuclei have been removed. The transplants took, and while 40% to 50% of older eggs show chromosomal abnormalities, says Grifo, "the rate was only 15% with the transplants."
Grifo's eggs have not yet resulted in any births, but an upside-down version of the procedure has succeeded. At the St. Barnabas Medical Center in Livingston, N.J., Drs. Richard Scott and Jacques Cohen have been taking cytoplasm--the nonnuclear part of a cell--out of young women's eggs and injecting it into the eggs of older women. One egg with refurbished cyotoplasm has grown into babyhood; another birth is expected next spring.
While all these new techniques could mean more reproductive choices for the infertile, they could also create tricky ethical and legal issues. Indeed, almost every clinical advance in assisted reproduction leads to unforeseen dilemmas. Take ICSI, which on its face seems utterly benign. In some cases, male infertility may be caused by a genetic defect; helping a man with such a defect reproduce could result in passing the defect on to his son. Also, since sperm can be obtained surgically, they have in a few cases been recovered from men killed in accidents, and then used to father children--a legal quagmire, since the dead cannot give consent.
Egg freezing may actually ease one ethical dilemma. When clinics freeze test-tube embryos for later use, what happens if that use never takes place? If the parents divorce or die, who gets custody of the embryos? Courts have addressed both these thorny situations in specific cases, but no nationwide policy exists in the U.S.
Even trickier is the question of what to do with leftover embryos when the parents are done having children. In the U.S., clinics have parents specify beforehand how they want unused embryos handled. Some donate them to other infertile couples or to scientists for research. Others have them destroyed. But many individuals and institutions--most notably the Roman Catholic Church--consider these embryos to be human beings and their disposal equivalent to murder.
Substitute frozen eggs for embryos, however, and these problems go away. No one considers an unfertilized egg to be a human being (though the Catholic Church officially opposes IVF, as it does nearly all assisted-reproduction procedures, including artificial insemination). Moreover, there is no controversy about whom the egg belongs to. An unfertilized egg, after all, has no father.
But even as it eases one ethical controversy, egg freezing may exacerbate another. Menopause, doctors now know, simply marks the end of a woman's egg supply. Otherwise, her reproductive equipment can still function if supplied with hormone supplements. With IVF, hormones and another woman's egg, even a postmenopausal woman can give birth.