The likelihood of getting pregnant while on birth control varies significantly depending on the type of birth control method used and how correctly it is used. Effectiveness by Birth Control Type:
- IUDs (copper and hormonal) and implants are the most effective with less than 1 pregnancy per 100 women per year (<1% failure rate).
- Injection has a 4 to 6% chance of pregnancy per year.
- Oral contraceptives (the pill), patch, and vaginal ring have a typical use failure rate of 7 to 9%, meaning 7 to 9 women out of 100 may get pregnant in a year with typical use.
- Less effective methods like condoms, diaphragms, and spermicides have higher failure rates ranging from about 12% to over 20% with typical use.
Effectiveness of the Pill:
- The pill is about 99% effective with perfect use (taking it every day at the same time), but typical use reduces effectiveness to about 91%, leading to around 9 pregnancies per 100 women annually.
- Missing doses, vomiting or diarrhea shortly after taking the pill, or interactions with other medications can increase the chance of pregnancy.
- The pill works by stopping ovulation, thickening cervical mucus, and thinning the uterine lining, but its effectiveness depends heavily on consistent and correct usage.
No birth control method except abstinence is 100% effective, but long-acting methods like IUDs and implants have the lowest chance of pregnancy, while pill, patch, and ring require careful adherence to instructions for maximum protection.
