Let’s be clear: Hormonal birth control pills are awesome. They uncoupled passion from pregnancy in a way that men have taken for granted since, well, Adam and Eve. The oral contraceptive pill was an essential building block of the movement for women’s equality and has prevented countless unplanned pregnancies. Still, as any expert will tell you, oral contraceptives are not 100 percent effective. Few things are. Abstinence, sure, but that’s not realistic for most people. When taken correctly—on schedule, without missing a dose—the pill is 99 percent effective. 
But nobody is perfect, and so the pill only has a 91 percent effectiveness rating. Here are a few things you should avoid if you want to stay out of that dreaded 9 percent.
1. Taking a Progestin-Only Pill at Different Times Every Day
The combination hormone pill, which contains both estrogen and progestin, isn’t terribly time sensitive. But some women can’t take estrogen. There’s still a pill for them, but it only contains progestin, which makes it really important that they take the pill at the same time every day. 
Progestin-only pills work a little bit differently from their combined cousins. Estrogen/progestin pills both prevent ovulation and thicken cervical mucus. Progestin-only pills just do the second. That—along with thinning the lining of the uterus—is designed to prevent Sperm from meeting Egg. However, the cervical mucus returns to its natural, sperm-friendly state just three hours after the progestin wears off. That’s why it’s so important to take the minipill at precisely the same moment every single day. Otherwise, as cervical mucus thins out, your risk of pregnancy increases.
2. Combining the Pill With Certain Other Medications, Including Antibiotics and Drugs for Seizures and Migraines
The pill doesn’t necessarily play well with others. Certain medications that treat seizures do so by breaking down hormones faster. When hormones are in charge of preventing ovulation and blocking sperm, you definitely don’t want them broken down faster. (Unless you want a baby.) 
A few rare classes of antibiotics, including rifampicin and rifabutin, can mess with your system when you’re on birth control. As with all things health related, talk to your doctor, and be sure to tell them you take oral birth control.
3. Forgetting to Take Your Pill
Now we’ve arrived at the crux of the matter. You can’t expect it to work if you don’t take it as directed. Most women who get pregnant on the pill do so because, well, they weren’t on the pill when they got pregnant. Not practically speaking, anyway. 
“For most pills, if you are in the middle or toward the end of your pack you should be fine, but if it is the first day of active pills and you forget to restart, this might be a problem,” Nikki B. Zite, professor of obstetrics and gynecology surgery at the University of Tennessee Graduate School of Medicine, told Fox News. “The first week of pills after the placebos are the most important to stop the egg from developing.” 
It’s best never to miss a pill. Even the placebos can help women remember to take the pill every day, which is crucial in the early weeks of the pack. But if you skip the placebos, be sure you never miss the first active pills. They are the most critical. And always keep in touch with your doctors. Ask them about any possible side effects or risks associated with all of your medications. Remember: Birth control doesn’t do a darn thing to stop STDs.
