Efficacy of emergency oral contraception

Contrary to popular belief, emergency oral contraception is not that effective.

A low failure rate also is not necessarily indicative of efficacy.

These findings are validated in a systematic review1 in the journal Sexual and Reproductive Healthcare of recent comparative studies of the intrauterine device (IUD) versus oral hormonal methods as emergency contraceptives.

“The failure rate of emergency oral contraception is reported as 2% but the probability of pregnancy from a random act of intercourse is about 3% to 5%, and may even be lower depending on population,” said co-author Norman Goldstuck, MD, an honorary consultant in reproductive medicine at the University of Stellenbosch in Cape Town, South Africa, who has been interested in emergency contraception since 1976. “Based on relative risk then, the efficacy of the IUD is about 90%,” he said.

The authors searched Medline, PubMed, Popline, Global Health and ClinicalTrials.gov. Chinese references were obtained from the Wanfang database.

In total, 13 studies (4 in English and 9 in Chinese) conducted between August 2011 and January 2019 met selection criteria.

The included studies were limited to women aged 18 to 35 who were not using any type of contraception at the time of unprotected coitus.

Among the 960 insertions of 4 types of copper IUD (TCu 380A, TCu 220, MLCu 375, Cu-gamma 220), there were 2 pregnancies, for a failure rate of 0.104%.

The oral methods assessed were levonorgestrel (LNG) 1.5 mg, ulipristal acetate (UPA) 30 mg and mifepristone 10 to 50 mg dose, as well as the combination of ethinyl estradiol (EE2) 50 µg and LNG 250 µg.

There were 22 failures out of 1,453 emergency oral contraception users, for a failure rate of 1.51%.

The relative risk of failure for an IUD versus an oral method was 0.1376 (95% confidence interval [CI]: -0.03 to -0.58).

In addition, the 6-month to 12-month pregnancy rate for IUDs was 0% to 6%, as opposed to 2.7% to 12% for the oral methods.

“The review confirms that IUDs are significantly more effective than pills for emergency contraception,” Goldstuck told Contemporary OB/GYN®. “However, emergency IUDs unfortunately do not appear to be as well tolerated as oral emergency contraceptives when IUDs are the contraceptive of choice, for reasons which are still not clear.”

The investigators said the type of copper IUD used as an emergency contraceptive may be relevant, if it is intended to be used as a long-acting reversible contraceptive (LARC) thereafter.

Relatively high continuing pregnancy rates in both the IUD and oral contraceptive group were probably due to women in the oral method group not immediately following up with a reliable form of contraception and IUD users having device expulsions and requested removals.

Goldstuck noted that the review was completed before the publication of a study2 earlier this year in The New England Journal of Medicine,“which showed hormonal IUDs can also be used for emergency contraception,” he said. “This could be a game changer.”

Regardless, the authors stated that emergency contraception is not a solution to unintended pregnancy.

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Disclosure

Goldstuck reports no relevant financial disclosures.

References

Cheung TS, Goldstuck ND, Gebhardt G. The intrauterine device versus oral hormonal methods as emergency contraceptives: a systematic review of recent comparative studies. Sex Reprod Healthc. Published online March 23, 2021. doi:10.1016/j.srhc.2021.100615

2. Turok DK, Gero A, Simmons RG. Levonorgestrel vs. copper intrauterine devices for emergency contraception. N Engl J Med. 2021;

384:335-344. doi:10.1056/NEJMoa2022141