The birth control pill is a highly popular and effective method of preventing pregnancy, but it is not infallible. Understanding the different rates of effectiveness and the factors that can influence them is crucial for any user. The odds of an unintended pregnancy while on the pill depend significantly on how consistently and correctly it is used, a distinction referred to as "perfect use" versus "typical use."
Perfect vs. Typical Use: Understanding the Odds
The difference between perfect use and typical use is the most important factor in determining the actual risk of pregnancy while on the pill.
- Perfect Use: This describes the effectiveness of the pill when taken exactly as directed, every single day, at the same time, without fail. Under perfect use, birth control pills are over 99% effective at preventing pregnancy. This means that out of 100 people using the pill perfectly for one year, fewer than one will get pregnant.
- Typical Use: This reflects how the pill is used in the real world, accounting for human error, such as forgetting a pill, taking it late, or starting a new pack late. With typical use, the effectiveness drops to about 91%. This means that for every 100 people on the pill for one year, about 7 to 9 may become pregnant. The discrepancy between these two numbers illustrates that inconsistency is the primary reason for pill failure.
How Birth Control Pills Prevent Pregnancy
Birth control pills contain synthetic hormones (either a combination of estrogen and progestin or progestin only) that work in several ways to prevent pregnancy.
- Ovulation Suppression: The hormones stop the ovaries from releasing an egg, so there is no egg available for a sperm to fertilize.
- Cervical Mucus Thickening: The hormones thicken the mucus on the cervix, creating a dense barrier that makes it difficult for sperm to travel through and reach an egg.
- Uterine Lining Alteration: The pill thins the lining of the uterus. If a fertilized egg were to implant, it would have a more difficult time attaching and growing.
Factors That Can Reduce the Pill's Effectiveness
Several factors can compromise the effectiveness of birth control pills, increasing the odds of an unintended pregnancy. While inconsistent use is the leading cause, others include:
- Missed or Late Doses: The most common reason for pill failure. The exact protocol for what to do depends on the type of pill and how many doses were missed, but any deviation from the daily schedule increases risk.
- Illness: Severe vomiting or diarrhea can prevent the body from fully absorbing the pill's hormones. If this happens, it's advised to use a backup method of contraception.
- Medication and Supplement Interactions: Certain drugs can interfere with the pill's metabolism, reducing its effectiveness. Key examples include the antibiotic rifampin (used for tuberculosis), certain antiseizure medications, and the herbal supplement St. John's Wort. It is a myth that common antibiotics for infections like strep throat or UTIs reduce the pill's effectiveness.
- Bariatric Surgery: Some malabsorptive surgical procedures can affect how oral contraceptives are absorbed by the body, necessitating a different birth control method.
- Improper Storage: Exposing pills to extreme heat, moisture, or direct light can degrade the hormones, rendering them less effective.
What to do if you miss a pill
The action you take depends on the type of pill you are on:
- Combination Pill: If you miss one pill, take it as soon as you remember. You can take two pills in one day to get back on schedule. You do not typically need backup contraception unless you have missed pills earlier in the cycle. If you miss two or more pills, follow the instructions on your pill pack and use a backup method for the next seven days. Emergency contraception may be considered if pills were missed during the first week and unprotected sex occurred in the last five days.
- Progestin-Only Pill (Mini-pill): This pill has a much stricter window. If you take a pill more than three hours late, you must use a backup method for 48 hours (two days). If you have had unprotected sex in the last five days, emergency contraception should be considered.
Pill vs. Other Contraception Methods: A Comparison
To put the pill's effectiveness into perspective, here is how it compares to some other common contraceptive methods.
| Method | Perfect Use Effectiveness (%) | Typical Use Effectiveness (%) | Effort Required |
|---|---|---|---|
| Birth Control Pill | >99% | 91% | Daily Action |
| Implant | >99% | >99% | None (after insertion) |
| IUD (Intrauterine Device) | >99% | >99% | None (after insertion) |
| Injection (Depo-Provera) | >99% | 94% | Periodic (quarterly) injection |
| Contraceptive Patch | >99% | 91% | Weekly Application |
| Male Condom | 98% | 87% | Per-Act Action |
Tips to Maximize Your Protection
Consistency is the single most important factor for maximizing the effectiveness of your birth control pills. To minimize the risk of pregnancy, consider these tips:
- Set a Daily Reminder: Use a smartphone alarm, a dedicated app, or a smart watch to remind you to take your pill at the same time every day.
- Create a Routine: Take your pill in conjunction with a regular daily activity, such as brushing your teeth or eating breakfast.
- Keep Pills Visible: Place your pill pack in a spot where you are sure to see it, like on your nightstand or next to your toothbrush, but away from direct heat and moisture.
- Consult Your Doctor: Before starting any new medication or herbal supplement, confirm with your healthcare provider or pharmacist that it will not interact with your birth control.
- Have a Backup Plan: Keep a backup method of contraception, like condoms, on hand in case you miss a pill or become ill.
Conclusion
While the birth control pill is an extremely reliable method of contraception with an impressive perfect-use effectiveness rate of over 99%, the odds of getting pregnant increase with inconsistent or incorrect use. With typical use, about 7 to 9 women out of 100 experience an unintended pregnancy annually due to human error. To maximize protection, consistent daily use is paramount. Users should be aware of factors like missed pills, illness, and certain medication interactions that can reduce effectiveness. For those who find daily pill-taking challenging, highly effective long-acting reversible contraceptives (LARCs) like IUDs and implants offer minimal user error and are excellent alternatives to discuss with a healthcare provider.
