WHAT IT IS: Named after Landrum Shettles, M.D., Ph.D., a former associate professor of obstetrics and gynecology at Columbia University, this method proposes that the timing of intercourse and the use of specific positions can help determine a baby's sex.
HOW IT WORKS: Noting that the X-bearing (female) sperm are hardier and slower moving than Y (male) sperm, Dr. Shettles advises couples wanting a girl to have sex two or more days before ovulation. When the egg finally arrives, Dr. Shettles believes that there's a better chance that only the female sperm will remain to fertilize it. Other directives for conceiving a girl include using the missionary position, which deposits sperm farther from the cervix, thereby making the robust female sperm the odds-on favorite for surviving the longer trip. He also suggests that the woman avoid having an orgasm, as it increases the alkaline secretions that he says tend to favor male sperm.
Conversely, to have a boy, Dr. Shettles says that intercourse should occur as close to ovulation as possible to give the male sperm a fighting chance. He also maintains that the rear entry position is preferable because the sperm would be deposited closer to the cervix. And, in this case, he advises that the woman climax.
SUCCESS RATE: Many doctors claim there is no scientific basis for these techniques. "Methods for sex selection such as timing of intercourse, using certain positions, adopting a certain diet, and the like are quackery," says Dr. Stillman. But Dr. Shettles and David Rorvik, his coauthor of How to Choose the Sex of Your Baby, claim that readers who follow their advice have at least a 75 percent chance of conceiving the child of their choice.
COST: $13 -- the price of the book.
WHO IS ELIGIBLE: Anyone willing to follow the procedures.
RESOURCES: The book.