Can You Get Pregnant on Birth Control? Know Your Risks

Can You Get Pregnant on Birth Control? The Facts You Need to Know

Think birth control is 100% effective? Think again. Modern birth control methods in the form of pills, patches, and IUDs have been game changers in the world of contraception but, even when used perfectly, no form of contraception is 100% effective. Human error, medications, health conditions, or missed doses can all lead to birth control failure, leaving you unprotected. Take the birth control pill for example – with perfect use, the pill is 99% effective, but in reality, it is only about 91% effective. Your chances of getting pregnant on birth control are low, but never zero.

Understanding how birth control works – and what can make it fail – helps you minimize pregnancy risks. In this article, we’ll cover everything you need to know about the chances of getting pregnant when you’re on birth control. We’ll go over how different contraception methods can vary in effectiveness and even cover potential signs that your birth control has failed, along with common usage mistakes and what types of health events may interfere with your birth control’s effectiveness. It’s a common misconception to think that birth control is 100% effective. However, if you’re asking “Can you get pregnant on birth control?” the answer is a resounding yes. Read on for more detail about how and why it can happen. 

How Effective Is Birth Control? Comparing Different Methods

Different types of birth control vary in their success rates. Typically, methods that require the most input from you (e.g. taking a pill every day) are the least effective while “set it and forget it” methods like an IUD have less margin for error and are therefore more effective.

Clinical trials use a technique called the Pearl Index (or Pearl Rate) to estimate how effective each method is with perfect use. This method can also be used to estimate the effectiveness in typical use (i.e. with human error involved). The higher the number on the Pearl Index, the less effective that method is. 

This chart shows the effectiveness of each method for both perfect use and typical use:

How Can Birth Control Fail? Key Risk Factors

Missed Pills or Late Doses

Consistency is what helps maintain contraceptive protection when it comes to oral contraceptive pills. For the combination pill, the one that contains both estrogen and progestin hormones, missing even two doses can increase your pregnancy risk. 

Pills that contain progestogen only (a hormone similar to progesterone) are very low dose and must be taken within the same time frame each day to remain effective. Some mini-pills must be taken within 3 hours of the same time each day, while others must be taken within 12 hours of the same time each day. 

What you do if you miss a pill depends on the type of birth control pills you are taking. In the next section we will detail specific guidelines for what to do if you miss a pill. 

Vomiting or Digestive Issues

Digestive issues like vomiting or diarrhea can interfere with the absorption of your birth control pill. If you vomit (or have serious “digestive issues”) within 2 hours of taking the pill, it may not have been fully absorbed into your bloodstream, thereby reducing its effectiveness. Take another pill straight away, but use additional contraception for 2 days after recovering.

Chronic digestive issues affect how well your body absorbs nutrients and medications. If the active ingredients in your birth control aren’t being absorbed properly, they won’t be as effective as they should be. Those with chronic digestive issues are often advised against using the pill for this reason. 

Medication and Supplement Interactions

There are a number of medications and supplements that interfere with birth control pills, making them less effective and leaving you unprotected. Antifungal medications, often used to treat skin infections, have a low risk of affecting your birth control pills, but it's worth checking out with your doctor if you are concerned. Anti-seizure medications are more nuanced and the interaction with certain birth control pills can make both drugs less effective.

There are a number of popular herbal remedies that may also affect how well your birth control works. For instance, St. John’s Wort is commonly taken to manage mild depressive mood, but research suggests an increased breakdown of estrogen in the body when you take this supplement, making your contraceptive less effective than you think. 

There’s a reason your doctor asks you what other drugs or supplements you are taking before prescribing anything new. Always check with your doctor, so your birth control is working the way you intended and there are no adverse interactions. 

Alcohol and Birth Control

Alcohol does not directly impact birth control in terms of reducing its effectiveness, but it can lead to other circumstances that may make your birth control less than effective. Regardless of the reason for vomiting (and alcohol intake can certainly be a reason), if you vomit within two hours of taking your birth control pill it may not be absorbed properly and thereby be less effective at preventing pregnancy. Alcohol can also impair judgment leading to riskier behaviors, including forgetting to take your medications, leaving you unprotected. And since hormonal birth control is processed in the liver, heavy drinking can affect liver function and potentially impact how well your body metabolizes medication. 

What to Do If You Miss a Birth Control Pill?

Consistency is what helps maintain contraceptive protection and missing your dose can put you at risk of an unplanned pregnancy. Mistakes happen, and missed doses can occur. Don’t panic; you can take practical steps immediately if you miss a pill.

If You Miss One Combination Pill

Missing one dose of the combination pill, the one that contains both estrogen and progestin hormones, is not usually a cause for concern. Simply take the missed dose and continue taking your pills as you usually do. Take the missed pill as soon as you remember, even if that means taking two pills in one day. If you’ve missed pills earlier in the pack, or in the last week of the previous cycle, your risk of an unplanned pregnancy increases slightly.

If You Miss Two or More Combination Pills

If you miss 2 or more pills in a row, you are at an increased risk for an unplanned pregnancy and should consider emergency contraception. Take the most recent missed pill, and then continue taking the rest of your pills on schedule. Use backup contraception, like condoms, for the next 7 days to ensure your protection. 

If You Miss a Mini-Pill (Progestin-Only Pill)

The mini-pill or progestin-only pills need to be taken at the same time every day to be effective in preventing pregnancy. If you miss a dose of the mini-pill, take the missed dose right away. If you are more than 3 hours late in taking the missed dose, you are at an increased risk of pregnancy and should use a backup method of birth control for the next two days, or avoid sex altogether. 

Emergency Contraception: What to Do If You Had Unprotected Sex 

Emergency Contraceptive Pills (Plan B, Ella)

Emergency contraceptive pills (ECPs) are a type of medication you can take to help prevent pregnancy. Even though they are often called “the morning after pill,” they do not need to be taken in the morning. Different ECPs work in different ways and therefore have different levels of effectiveness.

One of the most well-known ECPs is called Plan B. Plan B is most effective when taken within 72 hours of unprotected sex. The sooner you take Plan B the more effective it is and it works best when taken within 24 hours. Plan B side effects include nausea, abdominal pain, fatigue, and headaches but are usually mild and go away relatively quickly.

Morning after pills, like Plan B, contain levonorgestrel and work by delaying ovulation to prevent a pregnancy. They don’t work as well for heavier bodies, with the sweet spot being around 165 pounds. If you weigh more than that, they may not work as well as intended but there are other options to consider. 

Another ECP option is pills that contain ulipristal acetate rather than levonorgestrel. The most common brand of this type of pill is called Ella, and although it should be taken as soon as possible, it can be taken within 5 days (120 hours) of unprotected sex. Like Plan B, it works by delaying ovulation, but it can also make it harder for a fertilized egg to attach to the uterine lining so it can be taken even after ovulation. 

Emergency IUD for Pregnancy Prevention

Not everyone is a candidate for the morning after pill, in which case you may be able to use an intrauterine device (IUD). A copper IUD, which is non-hormonal, is actually the most effective method of emergency contraception. It can be inserted up to 5 days after unprotected sex and works by stopping sperm from reaching and fertilizing an egg, and making it harder for a fertilized egg to implant. When inserted within 5 days of unprotected sex, the copper IUD is more than 99% effective in preventing pregnancy. You’ll need an appointment to have it inserted, but it’s an excellent option for those wanting long-term birth control after an emergency situation. 

Early Pregnancy Signs While on Birth Control

The earliest symptoms of pregnancy can be easy to miss while on birth control. This is because many of the side effects of birth control are similar to the early symptoms of pregnancy, making it difficult to know whether you’re pregnant or just experiencing birth control side effects. 

In general, those early signs of pregnancy include a missed period, nausea, breast tenderness, fatigue, and headaches. Since your hormone levels are altered in both pregnancy and while on birth control, it’s common to experience similar side effects and miss the early signs. 

Tracking your fertility can help you understand where you are in your cycle and what that looks like, so you can see if you’re experiencing hormonal fluctuations, cycle irregularities, or you might be pregnant. It can be as simple as using a free app, like the Mira App, to track dates and monitor symptoms, or something more advanced like a hormone monitor. The Mira Hormone Monitor can measure key fertility hormones and their metabolites in urine with up to 99% accuracy. By taking daily tests with our Wands, you can track ovulation, identify your fertile window, and understand your unique hormone patterns over time. Another option for fertility awareness that can be used alone or in combination with other methods is basal body temperature tracking. By tracking changes in your basal body temperature with a special thermometer, you can attempt to detect when ovulation has occurred. Mira’s own BBT thermometer can be an excellent way to get to know your body better and learn more about your unique cycle patterns. Elevated BBT levels are also an early symptom of pregnancy, so tracking BBT can be helpful for detecting a very early sign that you are pregnant.

How Birth Control Side Effects Can Mimic Pregnancy Symptoms

Many birth control side effects mimic early pregnancy symptoms. Birth control side effects include changes to your cycle and bleeding patterns. Light bleeding may be your period, or it may be implantation bleeding and can be hard to tell the difference. While some birth control methods stop periods entirely so it can be confusing as to whether you’re experiencing getting pregnant on the pill symptoms or a side effect of your birth control.

When to Take a Pregnancy Test

Timing matters when it comes to taking a pregnancy test. False negatives are common if you test too early. Pregnancy tests detect human chorionic gonadotropin (hCG), a hormone produced approximately 6-12 days after fertilization.

If you’re tracking ovulation, you can use this information to calculate days past ovulation (DPO) to identify the optimal DPO for an accurate early pregnancy test. The best time to take a pregnancy test is after a missed period since enough time will have passed since you had unprotected sex for the hCG hormone to be present in your urine. The earliest pregnancy test that you can take is after 6-12 days have passed since ovulation. This gives your body enough time to produce enough hCG to be detected by a pregnancy test. 

If you’re using our Mira Hormone Monitor, you’ll have precise ovulation tracking to help you avoid testing too early and reduce the likelihood of false negatives. 

How to Prevent Pregnancy While on Birth Control

Take Your Pill at the Same Time Every Day

To keep your hormone levels consistent, take your pill at the same time every single day. There are plenty of reminder apps to help you remember. Or, you can pair it with an activity that you do every day at a specific time – such as right before you brush your teeth in the morning. This is especially important for progestin-only pills, since hormone levels can drop quickly and you may ovulate, which increases your chance of getting pregnant.

Use Backup Protection in High-Risk Situations

If you made a mistake, like missing a pill, or have had a situation that may affect the effectiveness of your birth control it’s best to use backup protection. Certain medications may reduce the effectiveness of your birth control, especially if they’re absorbed through your digestive tract. This is especially true if you vomit, as the medication may not have entered your bloodstream sufficiently to be effective. 

Consider Longer-Acting Contraceptives

If you struggle to take your pill at the same time every day, or if your lifestyle simply doesn’t allow it, consider other effective birth control methods. IUDs, implants, and the birth control shot all require less daily effort than pills and they typically have a higher effectiveness rate. 

Avoid St. John’s Wort and Certain Medications

St. John’s wort is a popular herbal supplement available in teas, tablets, liquids, and as a cream. It’s often used to manage depressive mood or menopausal symptoms, but it also interacts with other medications and can cause serious side effects. Among the interactions, the effectiveness of birth control is greatly reduced when taking this supplement. It’s been well known to disrupt oral contraceptives, but it may also make other hormonal contraceptives ineffective as well. If you’re on any other medications, check that they won’t affect your birth control or consider switching methods. If you have any questions or concerns, check with your doctor and they will be happy to assist you.

Final Thoughts

Can you get pregnant on the pill? Yes! As we’ve learned, the chances of getting pregnant on the pill, IUD, patch, or shot are low but not zero. Common mistakes like missing doses, or not taking your medication at the same time each day can lead to birth control failure and a potential pregnancy. If you’ve made a mistake there are emergency contraceptive options available, but you’ll need to act fast as they need to be taken within a certain time frame. Prevent birth control failure by following our tips for taking contraceptives and learning more about your fertility. 

Frequently Asked Questions 

Do you ovulate on birth control?

No, not usually. Most forms of birth control work by preventing ovulation. Progestin-only pills also stop ovulation but not consistently and about 4 in 10 people will still experience ovulation on progestin-only pills. 

What happens if you take birth control while pregnant?

There is little risk if you take birth control while pregnant. Some research has suggested that it could increase the risks of low birth weight or preterm birth, but this has not been proven by healthcare providers. 

How effective is birth control?

Some methods of birth control are more effective than others. With perfect use, most forms of popular birth control (implant, IUD, pill, patch) are 99% effective at preventing pregnancy. The NHS provides a more detailed breakdown of the effectiveness of different types of birth control. 

Can birth control make you infertile?

No. Birth control provides a temporary reduction in fertility, but it is not a cause for infertility and taking birth control does not lead to infertility.