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Cultured males

点击量:   时间:2019-03-07 11:09:15

By Nell Boyce AN INCREASINGLY popular form of IVF skews the sex ratio in favour of baby boys, say researchers in Barcelona. Improved culture techniques now allow fertility specialists to grow embryos in a dish for five days rather than the conventional three (This Week, 17 October 1998, p 22). This cuts down the risk that women undergoing IVF will have triplets or quadruplets, because embryos that survive to five days in culture are more likely to implant successfully. As a result, fewer embryos need to be introduced into the womb at each attempt to establish a pregnancy. Dairy researchers were the first to notice that culturing embryos for longer results in more male births. They found that technicians were selecting the most vigorous, rapidly dividing embryos—and for some reason these are more likely to be male. Anna Veiga of the Dexeus University Institute in Barcelona and her colleagues have now shown that the same holds true for humans. They analysed the sex ratio of children born from embryos cultured for five days at three Spanish fertility clinics. Of 514 babies, 57 per cent were boys, the researchers report in the latest issue of Fertility & Sterility (vol 72, p 221). Barry Behr, an IVF specialist at Stanford University in California, says Veiga has confirmed what many people already suspected. “Now that there’s a publication, it’s our duty to tell parents,” he says. But Behr suspects that most will still prefer the extended culturing technique,