Naturally, we can't be sure what the fastest birth is, because we busy humans haven't been keeping records of these things since the beginning of time. But there are a few modern examples of births that were so speedy (not to say easy or fun) that would be difficult to beat.
The first case was from 2007, when a woman from Great Britain had her baby less than two minutes after her water broke [source: Daily Mail]. While that family was looking for Guinness World Records authentication for the feat, another woman from Great Britain might've beat her by having her little one in a matter of seconds.
In 2009, Katherine Allen was having regular contractions at seven-and-a-half minutes apart, prompting her and her husband to make their way to the hospital. But as she was coming down the stairs to leave her home, her water broke -- and the baby came with it. Her 8-pound 5-ounce (3.8-kilogram) daughter slid down the leg of her sweatpants as she stood on the stairs, where dad heroically (and quite impressively) managed to catch the newborn [source: Daily Mail].