The birth control shot (such as Depo-Provera) is about 99% effective at preventing pregnancy when used perfectly—meaning you get the shot every three months as directed. However, with typical use, including occasional late shots, its effectiveness drops to around 94% , meaning about 6 out of 100 people using the shot may get pregnant in a year.
How it Works
- The shot contains the hormone progestin that prevents ovulation.
- It thickens cervical mucus to block sperm.
- It thins the uterine lining to prevent implantation of a fertilized egg.
Key Points on Effectiveness
- If received within the first 5 days of the menstrual cycle, it works immediately.
- If the shot is late by more than 2 weeks, the risk of pregnancy increases.
- Typical use effectiveness is approximately 94%, while perfect use is about 99% effective.
Considerations
- It must be administered every 3 months.
- It does not protect against sexually transmitted infections.
- Pregnancy might take some time (on average 10 months) to occur after stopping the shot.
- Side effects may include changes in menstrual bleeding, mood, appetite, and bone density with long-term use.
In summary, the birth control shot is a highly effective contraceptive method when used correctly on schedule but is slightly less effective with typical use due to timing adherence issues.
