Boy? Girl? Up To You

By Frederic Golden

The impulse to choose a baby's gender is probably older than human history, and prospective parents have tried no end of ingenious ways to do it. In ancient Greece, men would lie on their right side during sex to guarantee a boy; in 18th century France they would tie off their left testicle for the same result. Medieval Germans preferred to put a hammer under the bed to produce a boy, while their Danish cousins placed scissors there to make a girl. None of it worked, of course, and despite impressive advances in other aspects of reproductive science, modern medicine hasn't managed to do much better.

Not until now, anyway. Geneticist Edward Fugger and his colleagues at Genetics & IVF Institute, a fertility center in Fairfax, Va., surprised the obstetrical world last week with a report in the journal Human Reproduction asserting that the clinic can offer couples an 85% chance of ensuring they will have a girl. "I'm impressed," says Dr. Alan DeCherney, chairman of the department of obstetrics and gynecology at the UCLA School of Medicine and editor of the journal Fertility and Sterility. "It really seems to work."

IVF's breakthrough is based on the long-known fact that sperm have a gender, in a manner of speaking: some carry an X chromosome and some carry a Y. If the former fertilizes an egg, the baby will be a girl; if the latter, a boy. Over the years, fertility gurus have tried to boost production of X- or Y-bearing sperm through diet, or attempted to pick out Ys by their supposedly faster swimming speed or distinct electric charge--with dubious success.

The Virginia scientists, though, adapted a technique that has been used for more than a decade to select the sex of cows, horses and pigs. Working with U.S. Department of Agriculture scientist Lawrence Johnson, who invented the method, they stained sperm with a fluorescent dye that latches onto DNA. Measuring the glow of the sperm cells under laser light, they could gauge how much genetic material each one carried. As it happens, X chromosomes have about 2.8% more DNA than Ys. Once the sperm had been distinguished this way, an automated sorting machine separated the Xs from the Ys, and doctors could perform artificial insemination.

Why did it take so long to try the method in humans? The delay was not because of ethical concerns, though some have been raised (see Viewpoint), but because the DNA difference in animal sperm is larger, and thus much easier to measure.

About three years ago, the human experiment began in earnest. IVF recruited couples who wanted a child of a particular sex, either to bring "gender balance" to their family or to help them avoid sex-linked genetic diseases for which their offspring could be at risk. The procedure took no more than a day and cost a non-reimbursable $2,500 a try. "I actually watched the sperm enter my body on the screen of the ultrasound machine," marvels Monique Collins, 33, of Gainesville, Va., one of the program's first successes.

Although the technique yielded a relatively meager harvest of up to 300,000 sperm for each attempt (in contrast to 100 million or more in a natural ejaculation), the results were impressive. Of 14 pregnancies involving couples who wanted girls, the researchers report, 13 produced females. Says Fugger: "We're talking about increasing your chances of getting girls five- or sixfold." No formal report has yet been published on selecting a male baby, which, to the surprise of the scientists, was not the choice of most participants. But preliminary results suggest male selection will work 65% of the time.

As IVF perfects its technique and other clinics adopt it, the costs are expected to drop, putting gender choice within reach of hundreds of thousands of prospective parents. And considering that men were once willing to apply tourniquets to their testicles, it's hard to imagine that it won't become hugely popular.