Sex scared Marcus Whitlock. It was a tense, fraught ordeal. He couldn't get through it without being gripped by panic that it would lead to pregnancy. Then one day in April, Whitlock, an athletic 23-year-old college student in Illinois, says he walked into a doctor's office, told the receptionist he was 30, and had an hour-long consultation. A week or so later he returned, paid $850, and walked out after a 15-minute vasectomy. The way Whitlock saw it, he was free. He wouldn't have to worry anymore about whether his partner was on birth control.

About a hundred years ago, slash and yanks—so called because the original method involved cutting the scrotum and pulling out as much of the vas deferens tubing as possible before stitching it back up—were used mainly as supposed cures for tuberculosis and as part of eugenic schemes to sterilize men who were labeled crooks, cripples, or crazies. Even much later, after a less invasive no-scalpel technique was introduced in the United States in the mid-eighties, the surgery was considered an extreme measure. But lately, vasectomies are becoming the province of young, single men who claim to be tired of worrying about their partners' vigilance with the Pill. So rather than use condoms—less than ideal in terms of pleasure and, compared with vasectomies, which have an estimated 1 in 2,000 failure rate, only so-so on the contraception front—they're opting for a permanent fix.

"Now I can never have a girl say I made her pregnant," Whitlock says. "I don't have to worry about being tricked."

Or "oopsed," as some advocates of vasectomy put it—as in "Oops, I guess that was a breath mint, not a birth-control pill." The guy who views a vasectomy as a preemptive strike looks at certain tabloid stories through a twisted lens: When New England Patriots quarterback Tom Brady broke up with the actress Bridget Moynahan in 2006 and she announced shortly thereafter that she was having his child, this guy thought to himself, Sucker. He also likes to relate the story of Anna Cladakis, a Hooters promoter from Florida in her late thirties who's collecting $7,500 a month until the 18th birthday of the child she had by one of the founders of Outback Steakhouse. And if he had it handy, he'd point to a statistic like this one from a 2006 report by the Guttmacher Institute, a national think tank that focuses on reproductive issues: 3.1 million pregnancies—nearly half of all in the United States—are accidental.

But men opting to get vasectomies before the age of 40 aren't motivated only by an irrational fear of sneak pregnancies. They're also spurred by a philosophical argument: Why should women be in control of when—and if—they have children?

"A guy can tell an angry grandfather-to-be 'Look, here's money to take care of this at the clinic right now instead of dealing with this mistake for 18 years,'" says Doug Stein, a doctor in Florida who has performed more than 17,000 vasectomies over the past 30 years. "But only the woman's opinion matters. And some guys are sick of that."

Tim Vass, a 34-year-old technical writer in Florida, got snipped in May 2007 after a half-dozen pregnancy scares, including what he says were two attempted oopsings. Both of the latter were one-night stands; he says one woman admitted she didn't know who the father was and the other demanded a DNA test that proved her wrong. After his procedure, Vass experienced swinging-from-the-chandelier sex for the first time. "It's like eating junk food and knowing you're not going to get fat," he says.

It's the whiff of that kind of liberation that, according to testimonials on vasectomy- information sites, has guys throwing themselves post-procedure celebrations.

Elation, though, often gives way to regret. Although vasectomies are reversible—half of America knows Michael Scott of The Office got his reversed (and then got another one)—undoing them doesn't always restore fertility. And the likelihood of failure is greatest in those who have the procedure done when they're young and change their minds years later: Reversals are up to 80 percent successful, but if they're done more than 15 years after the vasectomy, that rate drops significantly. Of all snipped men, about 6 percent end up having reversals; according to Jay Sandlow, president of the Society for Male Reproduction & Urology, studies indicate that men who have vasectomies before the age of 30 are much more likely to want reversals than men who have them after that age.

The godfather of vasectomy in the Western World is Marc Goldstein, who brought the no-scalpel technique to New York after learning it in 1985 from doctors in central China's Chongqing Province, who developed it during the early years of the country's one-child policy. Every Friday he performs about three vasectomies at Weill Cornell Medical College on the Upper East Side of Manhattan. Each one costs $2,500 and takes around seven minutes. Before the procedure, patients go through a rigorous consultation, most of which consists of warnings. Warning: You'll have an ice pack on your balls for 24 hours. Warning: You also must wear a "scrotal supporter" for 48 hours. Warning: Your first postoperative ejaculations might be bloody. Warning: There may be heavy bruising and/or swelling. Warning: You will not be sterile right afterward; it takes 6 to 12 weeks or 15 to 20 ejaculations to clear out old sperm. Warning: According to Goldstein, you should consider your new infertility permanent.

And while the prospect of all that might be enough to deter some guys who are considering a precautionary vasectomy—even those susceptible to sneak-pregnancy hysteria—that could be about to change. According to Vincent Ciaccio, a spokesman for a social club for the child-free called No Kidding who got his vasectomy when he was 23, there are rumblings of experiments in China with a simple surgical procedure in which tubes are added to and removed from the vas deferens, which would allow for fully reversible infertility. If that happens, any perceived inequality between the genders when it comes to who's in charge of birth control could be eliminated. Get ready for equal-opportunity irresponsibility.

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