Call it nature, call it the biological imperative, call it irony. The truth is that your body generally wants to get pregnant … even if it’s not exactly on your to-do list. The species wants to survive, and we are Mother Nature’s pawns. (Of course, when we actually want to get pregnant, it’s not always that easy, but that’s a whole other story for a whole other article.)

Anyway, we often spend most of our younger reproductive years trying not to get pregnant, and we’re generally pretty successful. We’re informed, we know which birth control works best for us, and we’re aware of the common problems.

But here’s the thing: What you think you know about birth control may not necessarily be accurate. And a “surprise” pregnancy can be easier to come by than you may think. So before you do the deed again, check out this information about seven birth control mistakes. What are they? We’re so glad you asked.

Believe it or not, you can get pregnant …

Many breastfeeding moms don’t get their periods while nursing. This leads them to believe that they’re not ovulating and therefore can’t get pregnant. Nope! Using breastfeeding as birth control is called the lactational amenorrhea method (LAM), and often works when your baby is under six months old, you’re exclusively breastfeeding, and you haven’t yet gotten your first postpartum period.

Here’s the thing: We usually ovulate two weeks before we get our first period. So you can absolutely, 100 percent still get pregnant because your body can kick back into baby-making gear at any time. Plus, bouts of stress can decrease your milk supply, which in turn can increase fertility hormones. Personally, I don’t know any new moms who aren’t experiencing some sort of stress, so this birth control method seems like the baby equivalent of Russian roulette.

There’s a big, fat warning label on every pill packet that says taking antibiotics may lessen the efficacy of the pill, but many people don’t read the fine print. However, there’s only one antibiotic that’s been proven to interfere with the pill: rifampin, which is used to treat tuberculosis and bacterial infections. Scientists claim that there isn’t an issue when using other antibiotics. Their take is that pregnancy may occur because people may skip a pill or two when they’re not feeling well, or their bodies may not be able to absorb the hormones properly if they’re vomiting or have diarrhea. All that said, I know a decent number of pill-popping moms who’ve gotten pregnant while on antibiotics, so you probably don’t want to chance it.

If you swallow the pill, but vomit it back up, or send it out quickly with diarrhea, it doesn’t have a chance to get absorbed. So it’s like you didn’t take the pill at all.

While you have a less than one percent chance of getting pregnant by a man who’s had a vasectomy, you might have a much larger chance if you don’t wait until your partner’s been tested to see if it worked. Your partner’s sperm should be checked three months after the procedure, and he needs to have had a minimum of 20 ejaculations. Make sure to use other protection until you get the OK from your doctor after three months.

IUDs have a success rate of 99.7 percent, so pregnancy is very uncommon — but not impossible. One way to make sure you don’t end up in the small percentage of failures is to see your doctor a month after IUD insertion. Have your doctor make sure the IUD is still positioned correctly in your uterus. Also keep this in mind: With hormone-based IUDs like Mirena, some women don’t get their periods. But if you experience any traditional pregnancy symptoms like breast tenderness, morning sickness, or extreme fatigue, you should take a pregnancy test and call your doctor. IUD pregnancies carry a high risk of miscarriage and ectopic pregnancy, so you’ll want to talk to your doctor immediately.

They seem pretty easy to use, and hey, we all tested them out on bananas in Health class back in the day. How can anyone screw them up? Here’s the short list: using them with oil-based lubricants, like petroleum jelly or coconut oil, which erode latex; using expired condoms (yes, they have an expiration date) or any that have been exposed to extreme temperatures (don’t leave them in the glove compartment of your car in the cold of winter or heat of summer); accidentally ripping them with teeth, scissors, or a nail when opening the packet; not leaving enough room at the tip; and not pulling out (with the condom on, of course) quickly enough after sex. Maybe that’s not such a short list, after all.

Just because you’ve had infertility issues, it doesn’t necessarily mean you’re infertile. It could just mean that you have a very low chance of conceiving naturally … which means there’s still a chance.

According to one study in the journal Fertility and Sterility, 17 percent of women who had conceived through IVF subsequently got pregnant naturally shortly after. While researchers aren’t quite sure why this happens, some suggest that pregnancy kicks the body into gear and can also suppress the effects of conditions like endometriosis, allowing conception to happen more easily. Plus, pregnancy-related stress is at an all-time low since it’s the last thing on your mind until — surprise! If you’re not quite ready for a surprise, make sure to take the proper precautions.

Oh, yes, you read that right: You can get pregnant when you’re already pregnant. It’s called superfetation, and it’s very, very, very rare. (We’re literally talking about only 10 recorded cases ever.) It happens when a pregnant woman releases an egg a few weeks into her pregnancy and then has sex at just the right (or wrong!) time. This is so rare that the majority of women, myself included, won’t take precautions against it, but you should still know that it’s a thing.

So there you have it: seven ways you can get pregnant when you’re least expecting it. Be aware, be careful, and use this information to be fully in charge of your reproductive health.

Dawn Yanek lives in New York City with her husband and their two very sweet, slightly crazy kids. Before becoming a mom, she was a magazine editor who regularly appeared on TV to discuss celebrity news, fashion, relationships, and pop culture. These days, she writes about the very real, relatable, and practical sides of parenting at Her newest baby is the book “107 Things I Wish I Had Known with My First Baby: Essential Tips for the First 3 Months”. You can also find her on Facebook, Twitter and Pinterest.