BACKGROUND AND PURPOSE:

• Shen et al. (Cochrane Review, 2017) sought to determine which emergency contraceptive method is the most effective, safe and convenient to prevent pregnancy

METHODS:

• Systematic review and meta-analysis
• Pooled data from different databases and literature
• Primary outcome was observed number of pregnancies
• Secondary review outcomes were side effects and changes in menses

RESULTS:

• 115 trials with 60,479 women were included
• Pharmacologic emergency contraceptives were ranked as follows (from most to least effective)
  • Mifepristone
    • Mid-dose mifepristone (25 mg to 50 mg) associated with fewer pregnancies than low-dose (less than 25 mg)
  • Ulipristal acetate (a selective progesterone receptor modulator)
  • Levonorgestrel
    • Inconclusive whether single-dose levonorgestrel (1.5 mg) or two-dose regimen (0.75 mg 12 hours apart) is superior
  • Yuzpe method (estradiol-levonorgestrel combination)
• No statistical difference identified between Cu-IUD and mifepristone
• Nausea and vomiting
  • Yuzpe > Mifepristone
  • Yuzpe > Levonorgestrel
• Menstrual irregularities
  • Ulipristal acetate users are more likely than levonorgestrel to have delayed menstruation
  • Menstrual delay was more common with mifepristone than with any other intervention and appeared to be dose-related
• Obesity: The authors cite results from Jatlaoui and Curtis (Contraception, 2016) systematic review
  • Levonorgestrel
    • 4-fold increase risk of pregnancy in obese women (BMI ≥ 30 kg/m²) compared to BMI ≤ 25 kg/m²
    • At weight of 80 kg, pregnancy rate > 6% which is the same as probability without contraception
    • At weight < 75 kg, rate of pregnancy < 2%
  • Ulipristal acetate
    • 2-fold increase risk of pregnancy in obese women (BMI ≥ 30 kg/m²) compared to BMI <30 kg/m² but CIs wide and did not reach statistical significance
  • However, other analyses did not demonstrate consistent association when adjusting for other covariates

CONCLUSION:

• Levonorgestrel and mid-dose mifepristone were more effective than Yuzpe with fewer side effects
• Cu-IUD is the most effective emergency contraceptive along with mifepristone and the only method that will provide ongoing contraception and not weight sensitive
• With respect to obesity, data is considered limited and poor to fair quality but suggests reduced effectiveness, especially with levonorgestrel

Learn More – Primary Sources:

Cochrane 2017: Interventions for emergency contraception

Safety and effectiveness data for emergency contraceptive pills among women with obesity: a systematic review

Related ObG Topics:

Emergency Contraception: What, When and How?

IUDs and Implants: How to Manage Potential LARC Complications

Expert Opinion: Over-the-Counter Contraceptives for Adolescents