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
To read this article in full you will need to make a payment
Purchase one-time access:
Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online accessOne-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:
Subscribe to ContraceptionAlready a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
References
- Estimating the effectiveness of emergency contraceptive pills.Contraception. 2003; 67: 259-265
- Evaluation of a copper T200 as a post-coital contraceptive.Egypt Obstet Gyneacol. 1987; 13: 63-66
- Emergency contraception with Multiload Cu 375: a multicentre clinical trial.Contraception. 2001; 64: 107-112
- FFPRHC guidance (April 2006) emergency contraception.J Fam Plann Rep Healthcare. 2006; 32: 121-128
- Timing of sexual intercourse in relation to ovulation effects on the probability of conception, survival of the pregnancy and sex of the baby.New Engl J Med. 1995; 333: 1517-1521
- Attitudes of women in Scotland to contraception: a qualitative study to explore acceptability of long-acting methods.J Fam Plann Reprod Health Care. 2008; 34: 213-217
- What is it about intrauterine devices that women find unacceptable? Factors that make women non-users: a qualitative study.J Fam Plann Reprod Healthcare. 2006; 32: 89-94
- Progesterone receptor modulator for emergency contraception: a randomized controlled trial.Obstet Gynecol. 2006; 108: 1089-1097
- Ulipristal acetate versus levonorgestrel for emergency contraception: a randomized non-inferiority trial and meta-analysis.Lancet. 2010; 375: 555-562
- Minimum effectiveness of the levonorgestrel regimen of emergency contraception.Contraception. 2004; 69: 79-81
- Probability of pregnancy resulting from a single unprotected coitus.Fertil Steril. 1960; 11: 485-488
- Likelihood of conception with a single act of intercourse: providing benchmark rates for assessment of post-coital contraceptives.Contraception. 2001; 63: 211-215
- Estimating the efficacy of emergency contraception ��� how reliable are the data.Contraception. 2002; 66: 19-22
- New estimates of the effectiveness of the Yuzpe regimen of emergency contraception.Contraception. 1998; 57: 363-369
- The risk of conception on different days of the menstrual cycle.Popul Stud. 1969; 23: 455-461
- Additive splines in statistics proc stat comp.Am. Statistics Assoc. 1985; : 45-48
- Physical status: the use and interpretation of anthropometry. Report of a WHO Expert Committee. WHO Technical Report Series 854.World Health Organization, Geneva1995
- Low dose mifepristone and two regimens of levonorgestrel for emergency contraception.Lancet. 2002; 360: 1803-1810
- Advanced provision of emergency contraception has not reduced abortion rates in Lothian.Contraception. 2004; 69: 361-366
- The remaining barriers to the use of emergency contraception: perceptions of pregnancy risk by women undergoing induced abortions.Contraception. 2005; 71: 202-207
- The progestogen-only mini pill.Contraception. 1982; 26: 373-387
- Progestogen-only oral contraception. Findings in a large prospective study with special reference to effectiveness.Br J Fam Plann. 1985; 10: 117-121
- Body weight and risk of oral contraceptive failure.Obstet Gynecol. 2002; 99: 820-827
- Obesity and oral contraceptive pill failure.Contraception. 2009; 79: 334-338
- Ovarian suppression in normal-weight and obese women during oral contraceptive use.Obstet Gynecol. 2010; 116: 275-283
- Clinical effects of Norplant subdermal implants for contraception.in: Mishell D.R. Long-acting steroid contraception. Advances in human fertility and reproductive endocrinology. Vol 2. Raven Press, New York1983: 89-116
- Implantable contraceptives for women: effectiveness, discontinuation rates, return of fertility and outcome of pregnancies.Contraception. 2002; 65: 29-37
- Effectiveness of Norplant implants through seven years: a large scale study in China.Contraception. 1995; 52: 99-103
- Impact of obesity on oral contraceptive pharmacokinetics and hypothalamic-pituitary-ovarian activity.Contraception. 2009; 80: 119-127
- Obesity in pregnancy.Primary Care. 2009; 36: 341-356
- The need to take a ���new look��� at emergency contraception.J Fam Plann Reprod Healthcare. 2010; 36: 3-4
- Community pharmacists providing emergency contraception give little advice about future contraceptive use: a mystery shopper study.Contraception. 2010; 82: 538-542
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.
