Emergency Contraception in Obesity

Obesity is a body mass index of 30 or more. Patients with obesity can use every emergency contraceptive safely (category 1), but the oral options are less effective as weight rises. Levonorgestrel loses the most effect, ulipristal acetate keeps more, and the copper IUD is not affected by weight.

Mechanism of reduced effect. Greater body size lowers hormone exposure at the usual oral dose. Levonorgestrel acts only before the luteinising hormone surge, so any fall in exposure has a large effect.

Effectiveness. Reduced levonorgestrel efficacy is reported from body weight of about 70 kg and body mass index of about 30. Ulipristal acetate keeps more effect but also loses some at very high body mass index, about 35 and over. After oral emergency contraception in the general population, 1 to 2 in 100 women become pregnant. Rates are higher in obesity.

Copper IUD. Fewer than 1 in 100 women become pregnant afterwards, regardless of weight.

Return to fertility. Immediate.

Eligibility. Obesity is category 1 for emergency contraception. Cardiovascular disease, angina, migraine and severe liver disease are category 2 and may coexist with obesity.

History. Record weight and body mass index. Ask about malabsorptive bariatric surgery, because oral drugs may be poorly absorbed, and about enzyme-inducing medicines, which add to the loss of effect.

Choosing the option.

• Copper IUD first, within 5 days.

• Ulipristal acetate 30 mg next, within 120 hours.

• Levonorgestrel 1.5 mg when ulipristal acetate is unavailable. Levonorgestrel 3 mg as a single dose is used when neither the IUD nor ulipristal acetate is possible; evidence for this dose is limited.

Counselling points for the clinician. Explain that oral options may fail more often and that a pregnancy test at 3 weeks is important. Avoid weight-based judgement. Obtain consent and protect confidentiality. Offer condoms for dual protection.

Special groups.

• Adolescents with obesity: the same ordering applies.

• Postpartum: not needed before 4 weeks after birth.

• Breastfeeding: the copper IUD is preferred, because levonorgestrel is less effective at higher weight and ulipristal acetate passes into milk.

Regimens.

• Copper IUD: copper T 380A, inserted once within 5 days of intercourse or of expected ovulation. Immediate protection, lasts up to 12 years, no backup.

• Ulipristal acetate: 30 mg by mouth as one dose, within 120 hours. No progestin for 5 days after.

• Levonorgestrel: 1.5 mg by mouth as one dose within 120 hours; 3 mg as one dose when it is the only option.

Pregnancy exclusion. Pregnancy is reasonably excluded when there has been no unprotected intercourse since the last normal menses and menses are not overdue. A test is not needed before one recent episode.

Vomiting. Within 2 hours of a dose, repeat it with an antiemetic. After more than 2 hours, give nothing further.

Starting ongoing contraception. Choose a method that remains effective at higher weight.

• Copper IUD, levonorgestrel IUD and implant: category 1.

• Progestin-only pills: category 1.

• Injectable (150 mg intramuscularly every 13 weeks): category 1 in adults and category 2 from menarche to under 18 years.

• Combined pills: category 2.

• Timing after oral emergency contraception: pills the day after levonorgestrel (5 days after ulipristal acetate) with 7 days of backup for combined pills and 2 days for progestin-only pills; injectable the same day with 7 days of backup; implant within 7 days of the next menses.

Follow up. A pregnancy test 3 weeks after the episode if menses have not started, and earlier if menses are more than 7 days late.

Expected effects. Nausea, headache, abdominal pain, breast tenderness and altered menses.

Antiemetic regimen. Ondansetron 4 mg by mouth as one dose, repeated once after 8 hours if needed. Maximum 12 mg in 24 hours, for no more than 2 days. Limit to 8 mg in 24 hours in severe liver disease. No kidney adjustment is needed. Avoid in congenital long QT syndrome. In pregnancy use only when the benefit is clear. Short courses are acceptable in breastfeeding.

Failure. Oral failure is more likely. A positive test needs assessment for ectopic pregnancy when pain or bleeding is present. The dose does not harm the pregnancy.

Copper IUD insertion. Insertion can be harder in obesity and may need a larger speculum and good lighting. Analgesia: ibuprofen 400 mg by mouth 30 to 60 minutes before, once, maximum 1200 mg in 24 hours, avoided in peptic ulcer and significant kidney impairment.

Common errors. Offering levonorgestrel 1.5 mg alone without discussing the IUD, and assuming a normal pregnancy rate after oral doses.

Referral and escalation. Refer for severe lower abdominal pain, fainting or a positive pregnancy test with pain or bleeding.