Depot Medroxyprogesterone Acetate Contraceptive Failure Rate
The typical-use failure rate of depot medroxyprogesterone acetate (DMPA) is approximately 6% in the first year of use, though perfect-use failure rates are substantially lower at 0.3%. 1
Failure Rates by Use Pattern
Perfect Use vs. Typical Use
- Perfect-use failure rate: 0.3% - This represents women who return exactly on schedule every 13 weeks for reinjections 2
- Typical-use failure rate: 6% - This accounts for real-world adherence patterns including missed or delayed appointments 1
- Clinical trial data demonstrate failure rates ranging from 0% to 0.7% using Life-Table methods when administered precisely every 13 weeks 2
Real-World Effectiveness Data
- In population-based studies, contraceptive failure accounted for only 1.6% of discontinuations, corresponding to a failure rate of 0.9 per 100 woman-years 3
- The effectiveness depends entirely on the patient returning every 13 weeks (up to 15 weeks maximum) for reinjection 2
Comparison to Other Contraceptive Methods
DMPA's effectiveness places it in the "effective" category, superior to most user-dependent methods but below long-acting reversible contraceptives (LARCs): 1
- Highly effective (LARC): IUDs and subdermal implants <1% failure rate 1
- Effective: DMPA (6%), combined hormonal contraceptives (3-8%) 1
- Less effective: Condoms (12%), diaphragm (18%), spermicides (21%) 2
Critical Factors Affecting Failure Rates
Timing of Reinjection
- On-time or up to 2 weeks late (≤15 weeks): No backup contraception needed, full protection maintained 4, 5
- More than 2 weeks late (>15 weeks): Can still receive injection if reasonably certain not pregnant, but requires 7 days of backup contraception 4, 5
- Many providers schedule adolescents every 11-12 weeks to create a buffer for missed appointments, which improves real-world effectiveness 1, 4
Mechanism of Action
DMPA achieves its high effectiveness through multiple mechanisms: 6
- Inhibition of ovulation (primary mechanism)
- Thickening of cervical mucus
- Endometrial atrophy preventing implantation
- Serum MPA levels plateau at approximately 1.0 ng/mL for three months, maintaining contraceptive efficacy 6
Common Pitfalls That Increase Failure Risk
Patient-Related Factors
- Discontinuation due to side effects: 70% of discontinuations occur due to menstrual irregularities and weight gain, which increases pregnancy risk if alternative contraception is not immediately initiated 7, 3
- Failure to return for scheduled injections: Only 53% of users continue for 12 months or more in population studies 3
- Pre-injection counseling about expected menstrual changes significantly reduces discontinuation rates 1, 4
Provider-Related Factors
- Failing to counsel patients that backup contraception (condoms or abstinence) is required for the first 7 days after initial injection 1, 4
- Not scheduling follow-up appointments with adequate buffer time for adolescents 1, 4
- Inadequate counseling about the importance of returning on schedule every 13 weeks 2
Clinical Context
The 6% typical-use failure rate reflects real-world adherence challenges rather than method failure. When women receive injections on schedule, DMPA is one of the most effective reversible contraceptives available, with failure rates comparable to IUDs. 1, 2 The key to achieving optimal effectiveness is ensuring patients understand the critical importance of returning every 13 weeks and implementing systems (appointment reminders, flexible scheduling) to facilitate adherence. 4, 5
For women who struggle with appointment adherence, consider transitioning to LARCs (IUDs or implants) which have failure rates <1% and do not depend on regular clinic visits. 1