Abstract
Background
Emergency contraception (EC) does not always work. Clinicians should be aware of potential
risk factors for EC failure.
Study Design
Data from a meta-analysis of two randomized controlled trials comparing the efficacy
of ulipristal acetate (UPA) with levonorgestrel were analyzed to identify factors
associated with EC failure.
Results
The risk of pregnancy was more than threefold greater for obese women compared with
women with normal body mass index (odds ratio (OR), 3.60; 95% confidence interval
(CI), 1.96���6.53; p<.0001), whichever EC was taken. However, for obese women, the
risk was greater for those taking levonorgestrel (OR, 4.41; 95% CI, 2.05���9.44, p=.0002)
than for UPA users (OR, 2.62; 95% CI, 0.89���7.00; ns). For both ECs, pregnancy risk was related to the cycle day of intercourse. Women
who had intercourse the day before estimated day of ovulation had a fourfold increased
risk of pregnancy (OR, 4.42; 95% CI, 2.33���8.20; p<.0001) compared with women having
sex outside the fertile window. For both methods, women who had unprotected intercourse
after using EC were more likely to get pregnant than those who did not (OR, 4.64;
95% CI, 2.22���8.96; p=.0002).
Conclusions
Women who have intercourse around ovulation should ideally be offered a copper intrauterine
device. Women with body mass index >25 kg/m2 should be offered an intrauterine device or UPA. All women should be advised to start
effective contraception immediately after EC.
Keywords
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Article Info
Publication History
Published online: April 04, 2011
Accepted:
February 11,
2011
Received in revised form:
February 11,
2011
Received:
August 3,
2010
Identification
Copyright
© 2011 Elsevier Inc. Published by Elsevier Inc. All rights reserved.
