There was a german study in the past few years that revealed that the "pull-out" method was far more effective than what was previously known but the article was not heavily publicized to encourage this route of birth control. Also, this has got to be the most time tested form of birth control for thousands of years, right? Not saying its a top option, but its not like some of the comments above where people are shaking their head like "never"
I have been using the pull out method for almost 2 years just fine. We have sex 3-7 times a week. My girlfriend uses a product called "daysy" that is essentially a really fancy thermometer that tells her what part of her cycle she is in. Like what has been said above, she has to be ovulating for her to get pregnant. I have ejaculated in her many times when her daysy lights up green (meaning either safe to cum inside her or to not get pregnant. these devices are equally popular for getting pregnant and NOT getting pregnant) for 14+ days a month without any problems. I think most men, and a lot of women for that matter, are unaware that getting pregnant is not always so easy.
She was on birth control for 4 years before she had to stop because it made her sick, moody, and depressed. She is a much better person not on the pill. I am so happy we found a product like daysy. Nothing like having an orgasm together.