To get the facts, BuzzFeed spoke with Mary Jane Minkin, MD, who is a clinical professor of obstetrics, gynecology, and reproductive sciences at Yale School of Medicine. Take notes. 1. Letting him take the rear entrance. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Nickelodeon Yup, folks, it's true. A woman can get pregnant during anal sex. How can this be? During intercourse the semen doesn't always end up just in the rear. According to Minkin, “Even if he is penetrating rectally, he can be depositing a little seminal fluid around the opening to the vagina. Let’s face it, the vagina and the rectum are very close territory." 2. Opening a condom with your teeth. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Universal Pictures Two words: Slow down. In the heat of the moment, rushing and using your teeth to get the dang thing open is a no-no. You can accidentally puncture the condom without realizing it (same goes for scissors). Minkin suggests that you or your partner open it with your fingers on one of the notches. 3. Dry humping with your underwear on. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF NBC We all know dry humping without underwear can cause pregnancy, but did you know you can still get pregnant with your underwear on? Although rare, Minkin says it is possible if the man’s semen leaks through the opening of his boxers or the woman’s underwear gets pushed to the side, allowing an opening for the sperm to reach the vagina. 4. You can get pregnant when you're already pregnant. Walt Disney Mind = blown. This is strange (and uncommon) phenomenon is called superfetation, according to Minkin. It occurs when you're already pregnant and continue ovulating. The second fertilized egg implants in the lining of the womb, resulting in a second pregnancy. 5. Using oil-based lubes with condoms. Flickr: edandeddie Oil-based lubes and condoms don't mix. While many lubricants are completely safe to use with condoms, oil-based lubricants, like petroleum jelly, are not. According to Minkin, these types of lubes can degrade the latex and create microscopic holes in the condom, increasing your chances of getting knocked up. 6. Fooling around in the tub, without even having sex. Fox You can get pregnant in the pool or bathtub, even without putting the tip in! Minkin says, "Any time you end up with semen or seminal fluid around the vulva, you can get guys up inside there.” It's not super likely, but it's also not impossible. 7. Even if you take the pill regularly, you can still become pregnant. commons.wikimedia.org While it significantly decreases your chances of getting pregnant (over 99% in fact), it still isn't 100% effective — even if you never miss a pill. (This also applies to other forms of birth control, like the IUD, diaphragm, cervical cap, etc.) Minkin says, "Any contraceptive has a small failure rate associated with it." 8. When "sticky" fingers penetrate your vagina. amazon.com Minkin says if he just "finished" and still has some on his hand, it's possible his boys could find a new home...inside you. 9. Not leaving space at the tip of the condom. en.wikipedia.org Not leaving room at the tip could potentially cause sperm to spill out the sides, says Mikin. You get it. 10. When you have sex with a man who has had a vasectomy. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF 20th Century Fox Vasectomies are just like any other form of birth control, meaning they can't be 100% effective. Minkin says, "Vasectomies don't take effect immediately, so the urologist recommends having a follow-up semen analysis a couple of months afterwards to see if he is totally clear." In addition, it is possible for the snipped areas to grow back together. 11. It's even possible to get pregnant after you've had your tubes tied. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF COUB Just like a vasectomy, tubal ligation is also not 100% effective. Minkin says it can have up to a 1% failure rate. That being said, tubal ligation is still generally a great way to prevent pregnancy. 12. Having sex when you're on your period. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF HBO Sperm can live inside you for up to five days! That means if you have sex toward the end of your bleeding and you ovulate early, you could actually conceive, says Minkin. 13. If you take the morning-after pill. Instagram: @xavier43k Emergency contraception decreases your chances of getting pregnant, but it cannot totally prevent you from getting pregnant. Minkin confirms that if the pill is taken within a 24-hour window, it is about 95% effective. However, it gets less effective the longer you wait. Using regular contraception is more effective and cost-effective (one morning after pill can cost between $35–$60). 14. Using old condoms, especially those that have been exposed to hot and cold temperatures. Instagram: @elsieandelise These things don't last forever, people. If your partner whips a condom out of his wallet, you might want to think twice. Minkin recommends using a condom that is not expired, because over time the latex can weaken and lose elasticity. On that same note, a condom that has been exposed to hot and cold elements can also be compromised. 15. Tracking your fertility. Instagram: @postinfertility Don't get me wrong — fertility awareness is great. It is always a good idea to understand your body and to know approximately when you ovulate. But it isn't a guaranteed way to keep you from conceiving. Minkin says to remember that sperm can live inside you for up to five days, so even if you had sex when you weren't ovulating, you could ovulate a few days later and that sperm can still be there, upping the chances of conception. 16. Having sex when you're breastfeeding (obviously not at the same time). Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF 20th Century Fox If you think about all the families with babies born within 10 months of each other, clearly you understand breastfeeding is not 100% effective at preventing pregnancy. According to Minkin, the hormones involved in breastfeeding help suppress ovulation, but that doesn't mean you still can't get pregnant — even if you haven't started your period again after giving birth.