🔑 Key Learning

  • Emergency contraception (EC) prevents unintended pregnancy after unprotected sexual intercourse (UPSI).
  • 1st line: copper IUD is the most effective option and works even after ovulation. 
  • Ulipristal acetate (UPA-EC) is more effective than levonorgestrel (LNG-EC) at delaying ovulation.
    • Both oral EC methods are ineffective after ovulation.
    • Clinical judgement is needed as ovulation timing cannot be reliably confirmed in most patients.

🧬 Pathophysiology

Emergency contraception prevents pregnancy either by:

  • Inhibiting or delaying ovulation (oral methods).
  • Preventing fertilisation or implantation (Cu-IUD).

🌡️ Methods of Emergency Contraception

🧴 Copper Intrauterine Device (Cu-IUD)

  • Most effective method (<0.1% pregnancy rate)
  • Mechanism: toxic to sperm and ova, prevents fertilisation, inhibits implantation
  • Timing: insert within 120 hours (5 days) of UPSI, or up to 5 days after the earliest likely ovulation
  • Complications: uterine perforation (0.2%), expulsion (5%), pelvic inflammatory disease, ectopic pregnancy risk if failure occurs
  • Contraindications (UKMEC 4): unexplained vaginal bleeding, known/suspected pelvic infection, current STI, post-septic abortion, current pelvic inflammatory disease

💊 Ulipristal Acetate (ellaOne®) – 30mg single dose

  • Progesterone receptor modulator delays or inhibits ovulation
  • More effective than LNG-EC between 0–120 hours after UPSI
  • Should be taken ASAP after UPSI, ideally within 120 hours
  • Not suitable if:
    • Already ovulated (ineffective)
    • Concurrent use of liver enzyme inducers (PCBRASS drugs)
    • Severe uncontrolled asthma on oral glucocorticoids
    • Effectiveness could theoretically be reduced if a woman has taken progestogen prior to taking UPA-EC (e.g. missed pill).

💊 Levonorgestrel – 1.5mg single dose

  • Progestogen that delays ovulation
  • Licensed for use within 72 hours of UPSI (some guidelines say up to 96 hours but effectiveness decreases with time)
  • Can be considered if Cu-IUD and UPA-EC are contraindicated or not acceptable
  • Double dose (3mg) is recommended if  >70kg or >BMI 26kg/m2 
  • If on enzyme inducers and declines Cu-IUD: Double dose (3mg) can be considered if taking enzyme inducers, but evidence of efficacy is limited

💡 Choosing the EC Method

  1. 1st line: Copper IUD
    • Offer to all women where possible, as it works even if ovulation has occurred.
  2. If Cu-IUD is not acceptable or contraindicated:
    • Ulipristal acetate is preferred over levonorgestrel because of superior efficacy pre-ovulation.
    • Levonorgestrel is an alternative if UPA is contraindicated or the woman prefers it.
  3. Ovulation uncertainty
    • You cannot reliably determine ovulation in practice.
    • If mid-cycle UPSI (days 12–16 of a 28-day cycle), advise strongly towards Cu-IUD.
    • If early (days 1–10) or late cycle, oral EC is reasonable but explain reduced efficacy if ovulation has occurred.
  4. Enzyme inducers
    • Avoid UPA-EC.
    • Offer Cu-IUD.
    • If Cu-IUD not possible: consider double-dose LNG (3mg), but advise on reduced efficacy.
  5. Vomiting
    • If vomiting occurs within 3 hours of oral EC, repeat the dose.

📝 Exam Clues & Clinchers

  • Most effective EC: Cu-IUD within 5 days.
  • PCBRAS drugs: Avoid ulipristal; use Cu-IUD or double dose LNG.
  • Oral EC fails if ovulation has already occurred.
  • Vomiting within 3 hours → repeat dose.

🔗 Useful Links and References