Estimating emergency contraception efficacy with levonorgestrel and copper intrauterine devices

Area of Science:

• Reproductive Health
• Contraception
• Emergency Medicine

Background:

• Emergency contraception (EC) is crucial for preventing unintended pregnancies after unprotected intercourse.
• Intrauterine devices (IUDs) are effective EC methods, but their comparative pregnancy risk reduction needs further quantification.
• Levonorgestrel 52 mg IUD and copper T380A IUD are commonly used EC options.

Purpose of the Study:

• To determine and compare the observed versus expected pregnancy risk among users of levonorgestrel 52 mg IUD and copper T380A IUD as emergency contraception.
• To quantify the percentage of expected pregnancies prevented by each IUD type in a real-world EC setting.

Main Methods:

• Secondary analysis of a randomized trial comparing levonorgestrel 52 mg IUD and copper T380A IUD for EC.
• Inclusion of participants with at least one episode of unprotected intercourse (UPI) within 5 days of enrollment.
• Calculation of expected pregnancies using a validated method based on menstrual cycle day of intercourse, considering single and multiple UPI episodes.

Main Results:

• One pregnancy occurred in the levonorgestrel 52 mg IUD group (n=312), while no pregnancies occurred in the copper T380A IUD group (n=318).
• Levonorgestrel 52 mg IUDs prevented 93.2% to 95.7% of expected pregnancies.
• Copper T380A IUDs prevented 100% of expected pregnancies.

Conclusions:

• Both levonorgestrel 52 mg IUD and copper T380A IUD are highly effective for emergency contraception.
• Copper T380A IUD demonstrated complete pregnancy prevention in this cohort.
• The study provides valuable data on the real-world effectiveness of IUDs for emergency contraception.