How soon after replacing an Intrauterine Device (IUD) is contraception effective?

IUD Replacement and Immediate Contraceptive Effectiveness

When replacing one IUD with another IUD of the same type (copper-to-copper or hormonal-to-hormonal), contraception is effective immediately with no need for backup contraception. However, when switching between different IUD types or when specific timing conditions aren't met, backup contraception may be required for 7 days.

Immediate Effectiveness Scenarios

Copper IUD Replacement

• A copper IUD can be inserted at any time during the menstrual cycle and provides immediate contraceptive protection 1
• No additional contraceptive protection is needed when replacing a copper IUD with another copper IUD 1
• The copper IUD works immediately through its spermicidal effect on the intrauterine environment 2, 3

Hormonal (LNG-IUD) Replacement

If the LNG-IUD is inserted within the first 7 days since menstrual bleeding started, no additional contraceptive protection is needed 1

When replacing an existing LNG-IUD with a new LNG-IUD during this timeframe, contraception remains continuously effective 1

When Backup Contraception IS Required (7 Days)

LNG-IUD Insertion Timing

If the LNG-IUD is inserted more than 7 days since menstrual bleeding began, the woman needs to abstain from sexual intercourse or use additional contraceptive protection for the next 7 days 1

Switching Between IUD Types

When switching from a copper IUD to an LNG-IUD:

• If it has been >7 days since menstrual bleeding began, backup contraception is needed for 7 days 1
• Special consideration: If the woman has had sexual intercourse since the start of her current menstrual cycle and it has been >5 days since menstrual bleeding started, residual sperm might be in the genital tract 1
• In this scenario, consider providing emergency contraceptive pills (ECPs) at the time of LNG-IUD insertion 1

Clinical Algorithm for IUD Replacement

Step 1: Identify the Type of Replacement

• Same type (copper-to-copper or LNG-to-LNG): Proceed to Step 2
• Different types (copper-to-LNG or LNG-to-copper): Proceed to Step 3

Step 2: Same Type Replacement

• Copper-to-copper: Immediate effectiveness, no backup needed 1
• LNG-to-LNG within 7 days of menses: Immediate effectiveness, no backup needed 1
• LNG-to-LNG beyond 7 days of menses: 7 days backup contraception required 1

Step 3: Switching Between Types

• Copper-to-LNG within 7 days of menses: Immediate effectiveness 1
• Copper-to-LNG beyond 7 days of menses: 7 days backup contraception required 1
• LNG-to-copper: Immediate effectiveness regardless of cycle timing 1

Important Clinical Caveats

Residual Sperm Consideration

The most critical pitfall occurs when switching from a copper IUD to an LNG-IUD after recent intercourse 1. The copper IUD provides immediate contraceptive effect, but the LNG-IUD requires 7 days to achieve full contraceptive efficacy through cervical mucus changes 1. During this transition:

• Sperm can survive in the genital tract for up to 5 days 1
• If intercourse occurred >5 days after menses started, consider ECPs at insertion 1
• Alternatively, advise the woman to retain the copper IUD for at least 7 days after the LNG-IUD is inserted 1

Pregnancy Certainty

Before any IUD replacement, it must be reasonably certain that the woman is not pregnant 1. This is particularly important because:

• Pregnancy tests may not detect very recent conception 4
• Most qualitative urine pregnancy tests have sensitivity of 20-25 mIU/mL 4
• An additional 11 days past expected menses may be needed to detect 100% of pregnancies 4

Practical Management Strategy

When backup contraception is required, consider continuing the previous IUD for 7 days after the new LNG-IUD insertion, then removing the old device 1. This ensures continuous contraceptive coverage without requiring the patient to use additional methods 1.