title: Can we identify women at risk of pregnancy despite using emergency contraception? Data from randomized trials of ulipristal acetate and levonorgestrel.
abstract: BACKGROUND
  Emergency contraception (EC) does not always work. Clinicians should be aware of potential risk factors for EC failure.
  
  
  METHODS
  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/m(2) should be offered an intrauterine device or UPA. All women should be advised to start effective contraception immediately after EC.
authors.affiliation: University of Edinburgh, Scotland. anna.glasier@ed.ac.uk
authors.forename: Anna
authors.initials: A
authors.lastname: Glasier
authors.forename: Sharon T
authors.initials: ST
authors.lastname: Cameron
authors.forename: Diana
authors.initials: D
authors.lastname: Blithe
authors.forename: Bruno
authors.initials: B
authors.lastname: Scherrer
authors.forename: Henri
authors.initials: H
authors.lastname: Mathe
authors.forename: Delphine
authors.initials: D
authors.lastname: Levy
authors.forename: Erin
authors.initials: E
authors.lastname: Gainer
authors.forename: Andre
authors.initials: A
authors.lastname: Ulmann
mesh_terms: D044363:Contraception, Postcoital; D003277:Contraceptives, Oral, Combined; D005260:Female; D006801:Humans; D007494:Ireland; D016912:Levonorgestrel / Q000008:administration & dosage*; D015201:Meta-Analysis as Topic; D009649:Norpregnadienes / Q000008:administration & dosage*; D011247:Pregnancy; D018873:Pregnancy Rate; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D014481:United States; D014932:Women's Health Services
chemical_list: D003277:Contraceptives, Oral, Combined; D009649:Norpregnadienes; D016912:Levonorgestrel; C555622:ulipristal acetate