Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 12/28/2020
Worried about becoming pregnant? You’re not alone. According to the CDC, almost half of all pregnancies in the United States are unintended, meaning they occurred without any planning or expectation of becoming pregnant.
Although the pill, patch and other forms of hormonal birth control are very effective at reducing your risk of pregnancy, it’s still possible to get pregnant while you’re using birth control.
Below, we’ve explained what your risk of becoming pregnant is while you use the pill, patch or other forms of birth control. We’ve also discussed how common mistakes can hugely increase your risk of pregnancy, as well as the steps that you can take to protect yourself.
Most methods of birth control are highly effective at preventing pregnancy. However, they can become less effective if they’re used incorrectly, often by a significant amount.
Most birth control pills are 99 percent effective at preventing pregnancy if they’re used perfectly, meaning you take your pill on time every day, never forget pills and don’t take any medications that could interfere with the pill.
However, as we all know, human behavior isn’t perfect, meaning many people miss doses, take their pill too late in the day and make other mistakes. As a result, the “real-life” effectiveness of most birth control pills is about 91 percent on average.
This means that under perfect use, only one out of every 100 birth control pill users will become pregnant every year. Under typical real-life conditions, about nine out of every 100 birth control pill users will become pregnant every year.
Other forms of hormonal birth control are approximately as effective at preventing pregnancy as the pill:
The birth control ring, commonly sold as NuvaRing®, is 99 percent effective when it’s used perfectly and 91 percent effective under real-life conditions.
The birth control patch is equally effective, with a 99 percent effectiveness rate when used perfectly and a 91 percent effectiveness rate in real-life conditions.
The birth control injection, or Depo-Provera®, is 99 percent effective when used under perfect conditions and 94 percent effective in real-life conditions.
For the most part, the forms of birth control that require the least human involvement tend to be the most effective over the long term. For example, the IUD is more than 99 percent effective at preventing pregnancy once it’s fitted.
Similarly, the birth control implant, which is fitted into the arm and works for up to five years, has a more than 99 percent effectiveness rate.
On the other hand, the forms of birth control that rely heavily on human involvement are usually the least effective at preventing pregnancy in real-life conditions. For example, condoms are 98 percent effective when used perfectly, but only 85 percent effective under real-life use.
Don’t use one of the forms of birth control listed above? We’ve listed the effectiveness rates for other methods of contraception, as well as detailed information on birth control effectiveness, in our full guide to the most and least effective forms of birth control.
Used perfectly, hormonal birth control is very effective at preventing pregnancy. However, some mistakes can make birth control less effective, increasing your risk of becoming pregnant if you have sex. Common reasons your birth control may fail include the following:
Missing one or several birth control pills is one of the most common reasons for hormonal birth control failure.
Birth control pills prevent pregnancy by releasing certain hormones into your bloodstream. For example, combination birth control pills release a combination of ethinyl estradiol and progestin hormones to stop your ovaries from releasing eggs.
In order to keep your levels of these hormones consistent, you’ll need to take your pill every day without failure.
When you miss a pill, the amount of these hormones in your bloodstream drops, increasing your risk of becoming pregnant. Your risk of pregnancy increases even more if you miss several pills in a row.
Birth control pills come in two different types. There’s the combination pill, which contains a mix of ethinyl estradiol and a progestin hormone. Then there’s the progestin-only pill, or mini-pill — a lower-dose birth control pill that only contains a progestin hormone.
Some women prefer the progestin-only pill to the combination pill due to its reduced risk of side effects. We’ve looked at the advantages and disadvantages of each type of pill in our combined vs. progestin-only birth control pill guide.
If you use the progestin-only birth control pill, taking it at the wrong time of day could cause your hormone levels to drop, increasing your risk of becoming pregnant.
If you use a different form of hormonal birth control, such as the patch, ring or injection, it’s also possible to increase your risk of becoming pregnant by mistiming use of your birth control.
For example, if you use the birth control patch, you’ll need to replace it after seven days to keep your hormone levels consistent. If you keep your patch on for too long, or take it off and forget to replace it, you may have a higher risk of becoming pregnant.
If you vomit shortly after taking your birth control pill, your body may not have had enough time to fully absorb the hormones in the medication.
This can be a serious problem if you’re one of the many women who experience nausea after you start using the pill — a common side effect that may be caused by the ethinyl estradiol in many combined birth control pills.
The hormones in birth control pills need to be absorbed by your body before they’re effective at preventing pregnancy.
Like many other medications, most birth control pills are absorbed in your gastrointestinal tract, after which they’re metabolized in the liver by specific enzymes. Taking other medications that affect the same enzymes can lower absorption and make the birth control pill less effective.
Medications that can affect birth control pills include antibiotics such as rifampin and rifapentine, antifungal medications such as griseofulvin and several medications used to treat and manage epileptic seizures.
Many antiretroviral medications, including those used to treat HIV, can also affect the enzymes that metabolize hormonal birth control and reduce its effectiveness.
Finally, some health supplements and herbal remedies may interact with birth control pills and make them less effective. For example, the popular herbal remedy St John’s wort is linked to a higher risk of unexpected pregnancy in women who use oral contraceptives.
Because the birth control pill is absorbed through the digestive tract, your body may not properly absorb the hormones in the pill if you have acute or chronic diarrhea. This means that you may not be adequately protected from becoming pregnant.
Certain digestive conditions may also affect your ability to properly absorb the hormones in the pill. For example, some reports indicate that people with Crohn’s disease have a higher risk of oral contraceptive failure due to the effects of this disease on nutrient absorption.
If you use the birth control pill, patch or another type of hormonal birth control, there are several steps that you can take to reduce your risk of becoming pregnant:
Wait for your birth control to become effective before having sex. Some forms of birth control, such as the pill, ring and patch, can take several days to start working as contraceptives.
During this period, you’ll need to either avoid having sex or use a backup contraceptive method such as condoms to keep yourself protected.
Take your pill every day, on time. Almost all birth control pills come in a blister pack, with a specific day labeled for each pill. Follow the instructions provided with your pills and take them every day, making sure not to forget.
If you use the progestin-only pill, you’ll need to take it within the same three-hour time window every day. If you’re prone to forgetting, try setting an alarm on your phone to make timing your birth control pill easier.
If you miss a pill, follow the usage instructions provided with your birth control pills. Most of the time, you’ll need to take the missed pill as soon as possible. Check your birth control’s packaging to see exactly what you should do.
If you use the pill, make sure you always have a new pack ready. This way, you’ll always be ready to start your next pack once your current one runs out, reducing your risk of accidentally skipping a day or two because your supply isn’t available.
Consider a highly effective form of birth control. If you currently use condoms or another method of contraception that has a low real-life effectiveness rate, consider making the switch to one that’s more effective.
The pill, patch, ring and other forms of hormonal birth control are all easy to use and highly effective. Other methods of birth control, such as the IUD or implant, are even more effective and can last for several years after they’re inserted.
Use hormonal birth control and condoms. To keep yourself even more protected, it’s a good idea to use condoms whenever you have sex, even if you already use the pill or another form of hormonal birth control.
Not only will this reduce your risk of pregnancy even further — it will also keep you more protected from sexually transmitted diseases (STDs).
Check other medications for interaction risks. As we mentioned above, certain types of medication, including rifampin, griseofulvin, anti-seizure medications, HIV medications and St. John’s wort, can make the birth control pill less effective.
If you’re prescribed other medications, make sure to talk to your healthcare provider for information on interactions that could affect your method of birth control.
If you use birth control incorrectly, use an emergency contraceptive. If you’ve had unprotected sex and worry that you may not have used your birth control effectively (for example, you forgot to a pill beforehand), consider using emergency contraception.
Emergency contraceptives such as ulipristal acetate and levonorgestrel (sold as Plan B®) are highly effective when used correctly. However, you’ll need to use these medications quickly after having sex in order to make sure they’re effective.
When you’re pregnant, it’s normal to experience certain early symptoms and changes to your body. Common early signs and symptoms of pregnancy include:
Missing your period. Not getting your period is one of the most common early signs of pregnancy. However, there are many reasons why you may miss your period while you use birth control, with lots of these unrelated to pregnancy.
Fatigue. It’s very common to feel tired when you’re pregnant, even during the first week of pregnancy. This is caused by the hormonal changes that occur in your body after you become pregnant.
Mood swings. You may notice that your mood changes sharply. Like other symptoms of pregnancy, this is caused by changes in your body’s production of certain hormones.
Frequent urination. You might feel the urge to urinate more often than normal. This is caused by a hormone called human chorionic gonadotropin, which is produced during pregnancy to stimulate blood flow to your pelvic area.
Nausea and vomiting. It’s quite common to experience nausea and vomiting when you become pregnant — symptoms that are commonly referred to as pregnancy sickness, or morning sickness.
Breast tenderness. As early as one to two weeks after you become pregnant, you may notice that your breasts and nipples feel swollen and tender. Your breasts may begin to feel heavier and larger than normal as time passes.
Loss of appetite, or cravings for food. If you’re pregnant, you may suddenly find that you no longer enjoy foods you used to like. On the other hand, you may also experience cravings for certain foods.
It’s important to know that the symptoms listed above can also occur because of many illnesses and medical conditions, and having one or several of these symptoms doesn’t always mean that you’re pregnant.
However, if you’ve noticed any of the symptoms listed above and feel concerned that you could be pregnant, it’s important to seek advice and assistance.
To verify whether or not you’re pregnant, consider using a pregnancy test. You can either use a home pregnancy test or get a blood test from your healthcare provider. Both types of pregnancy test are accurate, although a blood test can detect pregnancy earlier than a home test.
If you’re pregnant, schedule an appointment to talk to your healthcare provider as soon as you can. They’ll be able to provide detailed information about the steps you can take to prepare for your pregnancy, including the changes you’ll need to make to your use of birth control.
Although hormonal methods of birth control like the pill, patch and ring are highly effective when they’re used perfectly, making mistakes such as forgetting a pill can increase your risk of getting pregnant.
It’s also possible to become pregnant even if you use your birth control perfectly. Although rare, even highly effective forms of birth control such as the IUD can fail from time to time.
If you’re concerned about becoming pregnant, the best approach is to protect yourself as much as possible using the methods listed above. For optimal protection, consider using condoms or another barrier contraceptive at the same time as your hormonal birth control.
Finally, if you’re concerned that you might be pregnant while using birth control, it’s important to talk to your healthcare provider as soon as possible.
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