What are the guidelines for switching from one birth control method to another, such as from a combined oral contraceptive (COC) to an intrauterine device (IUD) like Mirena (levonorgestrel-releasing intrauterine system) or a progestin-only pill (POP) like Micronor?

Switching Between Birth Control Methods

When switching from one contraceptive method to another, start the new method immediately without waiting for your next period, as long as you are reasonably certain the patient is not pregnant. 1

General Principles for All Switches

The CDC's U.S. Selected Practice Recommendations establish that immediate switching is safe and effective across all contraceptive methods. 1 The key consideration is determining pregnancy status and understanding backup contraception requirements, which vary by method type. 1

Switching TO Combined Oral Contraceptives (COCs)

Timing

• Start immediately if reasonably certain the patient is not pregnant—no need to wait for the next menstrual period. 1

Backup Contraception Requirements

• If ≤5 days since menstrual bleeding started: No backup needed. 1
• If >5 days since menstrual bleeding started: Use abstinence or backup contraception for 7 days. 1

Special Consideration When Switching FROM an IUD

If the patient has had intercourse since her current cycle started AND it's been >5 days since bleeding began, residual sperm could cause fertilization. 1 Choose one of these approaches:

• Keep the IUD in place for 7 days after starting COCs, then remove it. 1
• Use barrier contraception for 7 days BEFORE removing the IUD. 1
• Provide emergency contraceptive pills (ECPs) at the time of IUD removal. 1

Switching TO Progestin-Only Pills (POPs like Micronor)

Timing

• Start immediately if reasonably certain the patient is not pregnant. 1

Backup Contraception Requirements

• If ≤5 days since menstrual bleeding started: No backup needed. 1
• If >5 days since menstrual bleeding started: Use abstinence or backup contraception for 2 days. 1

Rationale for Shorter Backup Period

POPs achieve contraceptive effects on cervical mucus within approximately 48 hours, which is why only 2 days of backup is needed compared to 7 days for COCs. 1 However, POPs inhibit ovulation in only about half of cycles, making consistent daily timing critical. 1

Special Consideration When Switching FROM an IUD

If intercourse occurred since cycle start AND >5 days since bleeding began: 1

• Keep the IUD for 2 days after starting POPs, then remove it. 1
• Use barrier contraception for 2 days BEFORE removing the IUD. 1
• Provide ECPs at IUD removal. 1

Switching TO Mirena (Levonorgestrel-Releasing IUD)

Timing

• Insert immediately if reasonably certain the patient is not pregnant. 1

Backup Contraception Requirements

• If ≤7 days since menstrual bleeding began: No backup needed. 1
• If >7 days since menstrual bleeding began: Use abstinence or backup contraception for 7 days. 1

Special Consideration When Switching FROM a Copper IUD

If intercourse occurred since cycle start AND >5 days since bleeding began, consider providing ECPs at the time of Mirena insertion to address potential fertilization from residual sperm. 1

Pre-Insertion Requirements

Bimanual examination and cervical inspection are mandatory before IUD insertion. 1 No other examinations or tests are required in healthy women. 1

Algorithm for Managing Uncertain Pregnancy Status

When you cannot be reasonably certain the patient is not pregnant: 1

For hormonal methods (COCs, POPs):

• The benefits of starting likely exceed any risk—proceed with initiation. 1
• Schedule follow-up pregnancy test in 2-4 weeks. 1

For IUDs:

• Provide an alternative contraceptive method temporarily. 1
• Insert the IUD once pregnancy can be reasonably excluded. 1

Critical Pitfalls to Avoid

Timing errors: The most common mistake is miscalculating days since menstrual bleeding started, leading to inadequate backup contraception. 1, 2 Always count from the first day of bleeding.

IUD removal timing: Removing an IUD immediately when switching to hormonal methods after day 5 of the cycle creates a contraceptive gap if the patient had recent intercourse. 1 The 7-day (for COCs/LNG-IUD) or 2-day (for POPs) overlap or pre-removal abstinence is essential.

POP adherence counseling: Because POPs have rapid distribution and elimination (serum levels near baseline by 24 hours), taking them at approximately the same time daily is non-negotiable for effectiveness. 1 This differs from COCs, which have more pharmacokinetic forgiveness.

Continuing previous method: Consider having the patient continue her previous contraceptive method during the backup period when switching to ensure continuous protection. 1