From the Guidelines
Depo-Provera (medroxyprogesterone acetate) starts working as a contraceptive immediately if given within 7 days of menstrual bleeding, but if administered after 7 days, a backup contraceptive method like condoms should be used for 7 days after the injection. The injection works by preventing ovulation, thickening cervical mucus to block sperm, and thinning the uterine lining to prevent implantation 1. Depo-Provera is administered as a 150 mg intramuscular injection every 12-13 weeks (3 months). For maximum effectiveness, it's crucial to get your follow-up injections on time, as effectiveness decreases if you're more than 2 weeks late for your next dose. The contraceptive is highly effective when used correctly, but doesn't protect against sexually transmitted infections, so condoms may still be necessary depending on your situation. Some key points to consider when using Depo-Provera include:
- It can be started at any time, as long as the provider is reasonably certain the patient is not pregnant 1
- If started more than 7 days after menstrual bleeding, backup contraception should be used for 7 days 1
- It's essential to get follow-up injections on time to maintain effectiveness
- Depo-Provera does not protect against sexually transmitted infections, so additional protection may be necessary 1 The most recent and highest quality study, published in 2024, provides the most up-to-date guidance on the use of Depo-Provera 1.
From the Research
How Quickly Does Depo-Provera Start Working
- Depo-Provera (medroxyprogesterone acetate) is a highly effective contraceptive that starts working quickly after administration 2.
- Studies have shown that Depo-Provera causes profound changes in cervical mucus after injection, with a sharp decline in cervical mucus score within 6 to 24 hours after injection 2.
- By 24 hours after injection, 90% of subjects showed a poor cervical mucus score, indicating that the contraceptive is effective in preventing pregnancy 2.
- However, it is recommended that women use a backup method of contraception for 7 days after the first injection, as the exact timing of onset of contraceptive effectiveness may vary 2.
- The pharmacokinetics of Depo-Provera show that the progestin is detected in the serum within 30 minutes after an injection, and serum concentrations plateau at about 1.0 ng/mL for about three months 3.
- The contraceptive effectiveness of Depo-Provera is due to its multiple mechanisms of action, including inhibition of ovulation, thickening of cervical mucus, and atrophy of the endometrium 3.
Onset of Contraceptive Effectiveness
- The onset of contraceptive effectiveness of Depo-Provera is rapid, with changes in cervical mucus occurring within hours of injection 2.
- The exact timing of onset may vary depending on individual factors, such as the timing of the injection in relation to the menstrual cycle 2.
- Studies have shown that Depo-Provera is effective in preventing pregnancy within 24 hours of injection, but it is recommended to use a backup method for 7 days to ensure maximum effectiveness 2.
Return to Fertility
- After stopping Depo-Provera, return to fertility may be delayed for several months, as the progestin can be detected in the serum for up to nine months after a single injection 3.
- The time to return to ovulation and fertility varies depending on individual factors, such as the number of injections and the duration of use 4.
- Studies have shown that the median time to return to ovulation is around 30 weeks, with a 97.4% cumulative rate of return to ovulation at 12 months 4.