Done having kids? Thinking about permanent birth control? Here's what you should know about vasectomies.

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When former New York Jets cornerback back Antonio Cromartie underwent a vasectomy, he and his wife, Terricka, figured their babymaking days were behind them. "In my head we were good to go, we were having free sex!" Terricka told Us Weekly. "I really thought that his procedure was the best protection you could have at this point."

Um, not so much. Fast forward to January 2016, when the couple broke the news that they were expecting twins. Their surprise announcement underscored the common misconception that a vasectomy offers 100 percent protection against pregnancy. In fact, the failure rate for the procedure is about one in 2,000, but there's a lot you can do to decrease the risk of a pregnancy, particularly in the first few months afterward.

Considering a vasectomy? Here are five more things you need to know about this relatively simple in-office procedure.

1. He'll still be able to perform in bed.

Most guys are understandably squeamish about the idea of someone operating down there. And many "[believe] that it diminishes their sex drive and that things won't work normally" afterward, says Phillip Petree, author of The Man Puzzle, who also underwent a vasectomy.

But rest assured, those fears are unfounded. "All a vasectomy does is block the flow of sperm," explains Philip Werthman, M.D., a urologist and director of the Center for Male Reproductive Medicine & Vasectomy Reversal in Los Angeles. "It doesn't affect testosterone levels, erections, or orgasm." In fact, the only structure affected by the procedure is the vas deferens, the tubes that convey sperm from the testicles to the urethra. Those tubes are cut and sealed, so sperm can no longer travel through.

2. The procedure is pretty simple.

"Almost everybody walks out of here saying, 'That was no big deal,'" says Kevin Campbell, M.D., a urologist with The Urology Group in Cincinnati. "The procedure takes about 20 minutes, and 19 minutes of that is usually shooting the breeze while we do the procedure."

The procedure doesn't require any special prep beyond shaving the scrotum, which can be done at home ahead of time. In the office, the physician will inject a bit of lidocaine—the same stuff used to numb the mouth before dental work—into the scrotum. Once the area is numb, the physician makes a tiny incision in the scrotum and works on the vas deferens via that tiny hole. The cut is so small (about 2 to 3 millimeters long) that stitches aren't even required. Recovery typically takes just a few days, and men are instructed to avoid ejaculation for one week to allow healing.

3. You'll have to use another form of birth control for a few months.

As excited as you might be to ditch the Pill, IUD, or condom, you'll have to use a reliable form of birth control for about two months after a vasectomy. "I always tell people, 'I'm going to take the ammo out, but the gun is still loaded,'" Dr. Campbell says. That's because sperm travel from the testicles and down the vas deferens to the seminal vesicles, glands located near the prostate. A vasectomy blocks new sperm from reaching the seminal vesicles, but does not eliminate the sperm already there. "It usually takes somewhere between six to 12 weeks for all that sperm to die off or get flushed out," Dr. Werthman says.

4. Lab analysis of a semen sample is required before you get the all clear.

The only way to be certain a vasectomy has worked is to analyze ejaculate for the presence of moving sperm. Because the amount of time it takes for the body to clear sperm varies, most doctors have men bring in a semen sample two or three months post-procedure.

Some doctors give their patients the all clear after one clear (read: no sperm) sample, an approach endorsed by the American Urological Association. Other doctors want two clear samples, separated by a few weeks. Either way, it's perfectly normal if it takes you and your partner some time to trust your new method of birth control. "Even after my husband was tested and deemed 'blank,' it was hard for me to relax and feel totally confident," says Joanna N., a mom of two in Washington State.

5. Reversal is possible, but...

Before scheduling a vasectomy, make absolutely sure that neither of you wants more children. "If you're pretty sure you don't want any more children, don't get a vasectomy," Dr. Campbell says. The procedure is technically reversible, but there's no guarantee a reversal will be successful. And while there are other ways for a man to father a child post-vasectomy—via in vitro fertilization, for instance—both reversal and IVT are expensive and potentially time-consuming.

Of course, couples who keep these five factors in mind are likely to be very pleased with the results of a vasectomy. "It was the best decision I've ever made," Petree says. "It's simply liberating."