The problem with vasectomies is is that they're really hard to undo. Doctors recommend that men should only go for the snip if they are completely sure that the never want to have any more children. So they're a pretty bad option for anyone who isn't sure, or just wants to have kids later in life. But what would happen if men could turn their fertility on and off with just a 15 minute, pretty much painless, procedure?

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