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The contentious claim that sperm-sorting can improve a couple’s chance of having a child of the ‘right’ sex is under fresh attack. A team of Australian researchers claims to have ‘clearly demonstrated’ that techniques similar to those used at the London Gender Clinic do not effectively separate male and female producing sperm.

‘It is a very reliable study that uses definitive techniques,’ says John Aitken, a sperm expert at the Medical Research Council’s Reproductive Biology Unit in Edinburgh. The new work, says Aitken, suggests that ‘the kind of techniques gender selection clinics are using are probably not delivering what they claim they will deliver’.

Alan Rose, medical adviser to the London Gender Clinic, argues that the Australian team may not have followed the precise protocol his clinic uses. The London clinic, which opened just over a year ago, works under licence from the American scientist and entrepreneur, Ronald Ericsson, who reported in Nature in 1973 that he had developed a way of producing semen samples enriched in ‘male’ sperm (which bear Y chromosomes). Ericsson’s technique, now franchised to 55 clinics in the US alone, assumes that the slightly lighter ‘male’ sperm will be better able to swim through thick solutions of the protein albumin, compared to their heavier ‘female’ counterparts which bear X chromosomes.

The Australian researchers, led by scientist Sean Flaherty and doctor Huai-Xiu Wang at the University of Adelaide, took semen samples from 12 healthy volunteers and tried to separate the sperm using two different albumin methods, with either two or three layers of albumin. They report their findings in the latest issue of the American journal Fertility and Sterility.

In each case, contrary to Ericsson’s claims, the albumin treatment failed to produce samples enriched in Y-bearing sperm. In fact, the end result was slightly richer in X-bearing sperm, although the bias towards female sperm was only a matter of 1 or 2 per cent, and so was too small to be of any practical significance to prospective parents.

Earlier work in this field has been confused and contradictory, partly because of the unreliability of the staining technique previously used to detect Y-bearing sperm. Flaherty and his team used an up-to-date technique known as double-labelled fluorescence in situ hybridisation, which paints ‘male’ sperm green and ‘female’ ones red.

Rose of the London Gender Clinic says he has not yet had time to assess the Australians’ work. ‘But the final test is not a sperm test, but the live results,’ he argues. Pointing to the commercial success of the 55 American clinics, Rose says: ‘The fact of the matter is that the method seems to work. If it didn’t work, we’d be the first to stop using it.’ So far, 150 couples have paid several hundred pounds each for sperm-sorting and artificial insemination at the London Gender Clinic. Thirteen babies have been born as a result, but Rose is reluctant to say how many of these were of the ‘right’ sex. ‘We have not got enough babies yet to give a success rate,’ says Rose.

‘I personally don’t dispute Ericsson’s clinical results,’ says Flaherty. ‘But his technique does not appear to work by separating X and Y sperm. There may be other explanations for the clinical results.’ Flaherty speculates that the albumin could preferentially activate Y-bearing sperm. ‘But Ericsson doesn’t believe our results, and says we didn’t use his albumin.’

In the hopes of settling the controversy once and for all, the Adelaide team has now set up a double-blind trial in collaboration with a gender clinic in Chicago, with Aitken acting as the ‘honest broker’. ‘The idea is that the clinics in the US produce coded samples which they think are enriched with X or Y bearing sperm and send them to Australia for analysis,’ says Aitken. ‘The Americans send me the codes, and the Australians send me their analyses, and I put the two together.’ Aitken expects to ‘break the codes’ this month. Then he should know just how successful the clinics are in separating the girls from the boys.