What Are the Chances of Getting Pregnant on Birth Control?

While birth control is highly effective, no contraceptive method is 100% guaranteed to prevent pregnancy. Each method has a different success rate, and factors like forgetting a pill can increase the risk of pregnancy.

With typical use, the birth control pill has about a 7% chance of unintended pregnancy within the first year of taking it. With perfect use, this chance drops to less than 0.3%.

Understanding each method’s effectiveness and factors that increase the chances of an unintended pregnancy helps you choose which method is right for you.

Pregnancy Rates for Different Birth Control Methods

Before diving into unintended pregnancy rates, here is a review of birth control methods:

• Barrier devices: Condoms, sponges, diaphragms, and cervical caps.
• Emergency contraception: Pills (e.g., Plan B) or levonorgestrel-releasing or copper IUD placement after unprotected sex (also referred to as condomless sex).
• Fertility awareness: Track your cycle to identify fertile days and abstain from sex or use a barrier device while fertile.
• Hormonal: Pills, patches, shots, and vaginal rings that stop ovulation and thicken cervical mucus.
• Implants: A single rod your provider places under the skin in your upper arm releases hormones.
• Intrauterine device (IUD): Small, T-shaped devices placed in the uterus by your provider. They are available in hormonal or non-hormonal (copper) types.
• Lactational amenorrhea method (LAM): Exclusive breastfeeding for up to six months if you are not having periods.
• Spermicides: Gels or liquids that kill sperm.
• Sterilization: Permanent options like tubal ligation (female) or vasectomy (male).
• Withdrawal: The male partner pulls out before ejaculation.

Typical use rates are how well birth works with common mistakes, like missing a pill. Perfect use shows how well it works when you use it correctly every time. The table below shows the percentage of unintended pregnancies in the first year of typical use.

For comparison, around 85% of people who are sexually active and don’t use any form of birth control will become pregnant within a year.

Factors That Determine Your Chances

Long-acting methods, like intrauterine devices (IUDs) and implants, are over 99% effective because they work continuously. However, you must make an appointment with a healthcare provider to replace them when they are no longer effective. Implants last up to three years, hormonal IUDs last 3-8 years, and non-hormonal IUDs last up to 10 years. 

Using other methods, like pills or condoms, increases the chance of pregnancy because they depend on consistent use and are more prone to human error. Access to birth control and side effect tolerance also impact how likely you are to use these methods correctly. 

If you struggle with the side effects of specific birth control methods, try another method that better suits your lifestyle. For example, you might switch to a copper IUD if you don’t tolerate hormones well. Or, talk to a healthcare provider about getting an implant or IUD if you don’t want to remember to take a daily pill. 

What Reduces Birth Control Effectiveness?

The most common reason for reduced effectiveness is inconsistent or incorrect use. For example, you should:

• Change patches weekly
• Get shots every three months
• Replace rings monthly
• Take birth control pills at the same time every day

Condoms, diaphragms, cervical caps, and spermicides also require consistent and correct use. For example, you should:

• Avoid using expired products
• Choose the right size for a secure fit
• Get refitted for a diaphragm after having a baby
• Leave space at the tip of the condom
• Store them correctly (e.g., keep condoms in a cool, dry place)
• Use them every time you have sex

IUDs can also move out of place after insertion, especially in the first few months. You can check the IUD strings periodically to ensure they are still in place. 

What Could Cause Birth Control to Fail?

Hormonal Methods

Some birth control methods can fail due to incorrect use or timing, illness, medication interactions, or factors beyond your control. Examples of causes of failure while using hormonal methods include:

• Failure to replace an implant or IUD on time
• Missing a pill dose, patch change, or shot appointment
• Not taking the pill at the same time daily
• Sweating or friction causes a patch to fall off
• Vomiting shortly after taking birth control pills
• Not using alternate forms of birth control (like condoms) while waiting for hormonal birth control to work
  

Barrier Methods

Barrier methods can fail due to: 

• Condom breakage or slippage
• Improper fit of condoms, cervical caps, or diaphragms
• Slippage or removal of vaginal rings
• Using expired condoms or not using them
  

Timing or Withdrawal Methods

Timing errors can occur with: 

• Fertility awareness (e.g., improper tracking or not abstaining or using condoms during fertile windows)
• LAM (e.g., not breastfeeding exclusively or using LAM for the past six months)
• Withdrawal (e.g., lack of communication or control)

Vasectomy and Tubal Ligation

A vasectomy—a form of male birth control—can fail if one of the vas deferens (the tubes carrying sperm) doesn't fully close during surgery or if the tube reconnects over time. This procedure is not effective immediately. It requires a semen analysis three months after the procedure to confirm no sperm are present.

Tubal ligations—getting your "tubes tied"—can fail due to specific surgical techniques (like spring clips), tube reconnection, missed closure, or complex anatomy.

How to Tell If You May Be Pregnant

If you’re on birth control but think you may be pregnant, watch for signs like: 

• A missed period (or lighter than usual period)
• Fatigue (extreme tiredness)
• Frequent urination (needing to pee more often)
• Mood swings 
• Nausea 
• Sore or swollen breasts
  

Consider an at-home pregnancy test 10-14 days after unprotected sex—when you’d likely expect your period. Testing too soon may show a false negative, so if you’re unsure, retest after a few days. Or see a healthcare provider for a blood test.

Summary 

Birth control works best when you use it correctly and consistently. Some methods are more reliable than others, but missing dosages, not using condoms correctly, and taking certain medications with hormonal birth control can make them less effective. If you think your birth control didn’t work, emergency contraception may help, but it works best when you take action within five days of condomless sex. For those who think they may be pregnant, watch for signs like a missed period, fatigue, and nausea.