AN EXPERIMENTAL sperm-sorting technique designed to increase the odds of having a child of the desired sex has a fairly good success rate and does not appear to increase the risk of complications or birth defects, a fertility clinic says.
The Genetics & IVF Institute in Fairfax, Virginia, revealed the interim results of its ongoing clinical trial at a conference in Las Vegas earlier this month. The main findings? 鈥淔or girls this is very effective,鈥� says Keith Blauer of the institute. 鈥淔or boys it鈥檚 improving.鈥�
The technique, called Microsort, relies on the fact that the X-chromosome is larger than the Y. A fluorescent DNA dye is applied to sperm, and a machine called a flow cytometer separates them based on their relative brightness.
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In the trial, the overwhelming majority of couples requested a girl. Over 2000 sorts were done to pick out X-carrying sperm, compared with just 500 for Y-carrying sperm. Of the pregnancies obtained after sorting for X-carrying sperm, 90 per cent yielded girls. For boys the success rate was 80 per cent.
鈥淭he data to date is very reassuring,鈥� says Blauer. 鈥淭here is no evidence of an increased risk of major malformations.鈥� The rate of congenital abnormalities in the babies born so far is 2 per cent, similar to that in the general population.
鈥淎s far as we know it is safe, but until the experimental protocol is completed, we will not know for sure,鈥� says fertility specialist Stan Williams of the University of Florida in Gainesville. Even then, the results will not be considered definitive as the trial does not include a control group for comparison.
Other sperm-sorting methods are far less reliable. Pre-implantation genetic diagnosis is a more reliable technique than any sperm-sorting method, but its use for sex selection is controversial (快猫短视频, 12 June, p 6).