The copper intrauterine device is the most effective method of emergency contraception and may a good option for obese patients who have higher failure rates on oral emergency contraception, according to an updated practice bulletin from the American College of Obstetricians and Gynecologists.

Levonorgestrel emergency contraception may be less effective among overweight (BMI 25-29.9 kg/m2) and obese (BMI 30 kg/m2 or greater) women, and ulipristal acetate may be less effective among obese women. The copper IUD, however, is not affected by body weight.

“Consideration should be given to use of a copper IUD as an alternative to oral emergency contraception in obese women. However, oral emergency contraception should not be withheld from women who are overweight or obese because no research to date has been powered adequately to evaluate a threshold weight at which it would be ineffective,” ACOG officials wrote in a practice bulletin published on Aug. 19 (Obstet Gynecol. 2015;126:e1-11).

Among oral emergency contraception methods, ulipristal acetate is more effective than the levonorgestrel-only regimen and is effective for up to 5 days. But the levonorgestrel-only method is more effective than the combined hormonal regimen, with less nausea and vomiting.

The most common adverse effects for the pills are headache and nausea, as well as irregular menstrual bleeding. Less often reported effects include breast tenderness, abdominal pain, dizziness, and fatigue. Uterine perforation can occur in 1 of every 1,000 insertions of the copper IUD, which can also cause cramping and increased or painful menstrual flow.

The ACOG bulletin does not recommend a clinical exam or pregnancy testing before a patient uses emergency contraception. However, patients should be evaluated if their menses is delayed by a week or more after taking emergency contraception, or if they experience lower abdominal pain or persistent irregular bleeding, according to the bulletin.