The permutations of family relationships created by IVF seem endless. The latest twist comes with a Montreal woman's decision to freeze 21 of her eggs for her 7-year-old daughter, who is infertile because of Turner's syndrome. This means that Melanie Boivin would be the mother of her granddaughter and that her daughter Flavie would bear a child who would be her half-sibling.

Of course, the offer is merely hypothetical at the moment. No one even knows if the frozen eggs will be viable or whether Flavie will be interested. More current are the arguments supporting Melanie's very public announcement. The doctor involved, Professor Seang Lin Tan, was nonchalant about the controversy. "Ethical considerations change with time. The soonest the daughter will contemplate using the eggs will be 20 years from now. Who knows what the ethical attitudes will be even 10 years from now?" he asked.

De Sherman Silber, of the Infertility Center of St Louis, suggested that it was a mark of progress. "Those who object would probably have objected to the invention of fire by mankind hundreds of thousands of years ago." And bioethicist Arthur Caplan says concerns are unwarranted. "The dilemma of giving birth to one's genetic sister I think is overdone. I suspect parents will adapt quickly, adoptive parents who raise their sister's kids, or even a younger sibling."

Others were more cautious. "If the goal is to provide her with a family, why not make it less ethically challenging and consider either donor eggs or adoption?" suggested Dr Jeffrey L. Deaton, a North Carolina fertility expert. "Our technology is progressing more rapidly than our ability to understand the social, ethical and religious ramifications."