Doctors challenge new methods of granting an ancient wish
It is one of nature's most coveted secrets, and over the centuries many have professed to know it. Aristotle had a surefire formula: make love in the north wind to conceive a male child and in the south wind for a girl. Hippocrates had his own prescription—tie a string around the right testicle to stimulate the production of male seed, or the left, if a daughter is sought. Medieval alchemists had an even more exotic recipe for a son: a precoital drink of lion's blood and intercourse under a full moon.
While these theories have vanished into folklore, many prospective parents remain attracted by the idea that they might be able to choose the sex of their children.
In recent years scientists have attempted to take up where the philosophers and alchemists left off. The results have been disappointing. In the 1960s Dr. Landrum Shettles of New York City's Columbia-Presbyterian Medical Center created a sensation with his announcement that gender was influenced by the timing of conception within the menstrual cycle and by the acidity or alkalinity of the female reproductive tract. A douche of vinegar, he contended, would confer an advantage on sperm bearing an X chromosome (for females), while a douche of baking soda would shift the odds toward the Y-bearing sperm (for males). Shettles' theory has now been generally discredited.
The latest method that purports to select the sex of offspring is the brainchild of Ronald Ericsson, founder of Gametrics Ltd. of Sausalito, Calif. Ericsson, who has a Ph.D. in reproductive physiology, is the coauthor, with University of California Obstetrician Robert Glass, of a 1982 book, Getting Pregnant in the 1980s. Gametrics' aggressively marketed method has stirred popular interest, but many scientists are skeptical. "This could be Landrum Shettles all over again," says Dr. Joe Leigh Simpson, a spokesman for the American College of Obstetrics and Gynecology.
Ericsson's theory is based on the fact that sperm carrying the Y chromosome move somewhat faster than sperm carrying the X. To select males, a sample of semen is placed at the top of a glass column containing a solution of albumin, a sticky protein normally present in such bodily fluids as blood and semen. After an hour, more Y-containing sperm than sluggish Xs should have sped to the bottom. The Y sperm are further concentrated by being run through increasingly thicker solutions of albumin. "It's like making them run the Boston Marathon with overshoes on," says Ericsson. The prospective mother is then artificially inseminated with the Y-concentrated sperm. Ericsson claims that of 146 women who became pregnant by this method at clinics licensed by Gametrics, 112 bore males—a success rate of 77%.
Methods of selecting females are also being developed by Gametrics and others.