Emergency Contraception for a 90 kg Woman
For a 28-year-old woman weighing 90 kg who needs emergency contraception, ulipristal acetate (UPA) 30 mg is the most recommended approach, as levonorgestrel is essentially ineffective at this weight. 1
Weight-Based Efficacy Considerations
The critical factor at 90 kg body weight is that levonorgestrel loses effectiveness in women weighing >75 kg and becomes essentially ineffective above 80 kg, making it an inappropriate choice for this patient. 1 In contrast, ulipristal acetate retains full efficacy in overweight and obese women. 1
The CDC guidelines specifically note that levonorgestrel formulations might be less effective than UPA among obese women. 2
Recommended Options in Order of Preference
First Choice: Copper IUD
- The copper IUD is the most effective emergency contraception method overall and can be inserted within 5 days of unprotected intercourse. 2, 1
- It provides the added benefit of serving as highly effective ongoing contraception for up to 10 years. 2
- This option is weight-independent and maintains superior efficacy regardless of body mass. 1
Second Choice: Ulipristal Acetate 30 mg
- UPA is the preferred oral emergency contraceptive for this patient given her weight of 90 kg. 1
- It maintains efficacy throughout the entire 120-hour (5-day) window after unprotected intercourse. 2, 1
- UPA reduces pregnancy risk by approximately 42% compared to levonorgestrel when used within 72 hours, and by 65% when used within the first 24 hours. 1, 3
- It should be taken as soon as possible within the 5-day window for maximum effectiveness. 2, 1
Not Recommended: Levonorgestrel
- Levonorgestrel should be avoided in this patient due to her 90 kg weight, as it is essentially ineffective at this body mass. 1
- Even in normal-weight women, levonorgestrel effectiveness declines significantly after 72 hours. 2, 1
Practical Implementation
If UPA is chosen:
- Single oral dose of 30 mg taken as soon as possible. 1
- The patient can resume regular contraception immediately but must use barrier methods or abstain for 14 days or until next menses. 1
- A pregnancy test is recommended if withdrawal bleeding does not occur within 3 weeks. 1
- The most common side effect is headache (19% of users), and menses may be delayed by 2-3 days. 1
If copper IUD is chosen:
- Can be inserted up to 5 days after the first act of unprotected intercourse. 2
- When ovulation timing is known, insertion can occur beyond 5 days as long as it's within 5 days after ovulation. 2
- Provides immediate and ongoing highly effective contraception. 2
Key Clinical Pitfall
The major pitfall to avoid is prescribing levonorgestrel to women weighing ≥80 kg, as this represents ineffective treatment and a missed opportunity to prevent pregnancy. 1 Always assess weight when counseling about emergency contraception options.