Boy or Girl? You Decide Primitive, even brutal, methods of sex selection have existed for thousands of years. While folk remedies were largely useless, female infanticide and the abortion of unwanted fetuses have proven crudely effective. Previous scientific attempts at sperm sorting have also been a disappointment. One recent theory, that male-bearing sperm swim faster than female-bearing sperm, remains unproven. Now, doctors at a fertility clinic in suburban Washington, D.C., have developed a technique that they believe increases the likelihood that a couple can choose the sex of their baby, and in a much more agreeable way. The technique, developed by the Genetics & IVF Institute, takes advantage of the one difference between sperm carrying the X and Y chromosomes, The New York Times reports. Sperm carrying the Y chromosome, which produces males, contains 2.8 percent less genetic material than the sperm carrying the female X chromosome. The institute's method of sorting sperm based on the amount of DNA present has yielded impressive results. The researchers report that if they select for X-bearing sperm, they end up with samples carrying an X chromosome 85 percent of the time. The same selection for Y-bearing sperm turns up positive results in 65 percent of the cases.