Starting Depo-Provera: Backup Contraception Requirements
When starting Depo-Provera as a new contraceptive method, you should continue your contraceptive pill (or use another backup method) for 7 consecutive days after the injection if it is given more than 7 days after your menstrual period started. 1
Timing-Based Algorithm for Backup Contraception
The need for backup contraception depends entirely on when you receive your first Depo-Provera injection:
No Backup Needed:
- If the injection is given during the first 5-7 days of your menstrual cycle (counting from the first day of bleeding), no backup contraception is required 2
- The CDC guidelines specifically state that DMPA can be initiated during the first 5-7 days of a normal menstrual cycle with no backup contraception needed 2
7 Days of Backup Required:
- If the injection is given more than 7 days after your period started, you must use backup contraception (such as continuing your pill) for 7 consecutive days after the injection 1
- This is classified as treating it as a "new start" when given outside the optimal window 1
Scientific Rationale
The 7-day backup requirement exists because research demonstrates that:
- Ovulation suppression is not immediate when DMPA is given later in the menstrual cycle 3
- In a prospective study, 30% of women who received DMPA between days 8-13 of their cycle still ovulated, with all ovulations occurring within 3 days after injection 3
- Women receiving injections on days 8 or 9 had better ovulation suppression than those receiving it on days 10-13 3
- Cervical mucus changes (which provide contraceptive protection) occur within 24 hours in 90% of women, but this alone is insufficient protection against pregnancy 2
Critical Considerations
Emergency contraception should be considered if you had unprotected intercourse in the 5 days before receiving the Depo-Provera injection, especially if the injection was given during the first week of your cycle 1
The CDC recommends immediate initiation (giving the injection at any time if reasonably certain you're not pregnant) rather than making you wait for your next period, as delaying DMPA initiation was associated with more unintended pregnancies than immediate receipt 2, 4
Common Pitfall to Avoid
The most significant error is assuming immediate contraceptive protection when starting Depo-Provera mid-cycle. Unlike when given during menses, mid-cycle initiation requires the full 7-day backup period because ovulation may not yet be suppressed 3. Do not discontinue your current contraceptive pill prematurely if you receive the injection outside the first week of your cycle 1.