title: Injectable contraception: what should the longest interval be for reinjections?
abstract: BACKGROUND
  Progestin-only injectable contraceptives continue to gain in popularity, but uncertainty remains about pregnancy risk among women late for reinjection. The World Health Organization (WHO) recommends a "grace period" of 2 weeks after the scheduled 13-week reinjection. Beyond 2 weeks, however, many providers send late clients home to await menses.
  
  
  METHODS
  A prospective cohort study in Uganda, Zimbabwe and Thailand followed users of depot-medroxyprogesterone acetate (DMPA) for up to 24 months. Users were tested for pregnancy at every reinjection, allowing analysis of pregnancy risk among late comers.
  
  
  RESULTS
  The analysis consists of 2290 participants contributing 13,608 DMPA intervals. The pregnancy risks per 100 women-years for "on time" [0.6; 95% confidence interval (CI), 0.33-0.92], "2-week grace" (0.0; 95% CI, 0.0-1.88) and "4-week grace" (0.4; 95% CI, 0.01-2.29) injections were low and virtually identical.
  
  
  CONCLUSIONS
  Extending the current WHO grace period for DMPA reinjection from 2 to 4 weeks does not increase pregnancy risk and could increase contraceptive continuation.
authors.affiliation: Family Health International, Research Triangle Park, NC 27709, USA. msteiner@fhi.org
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Steiner
authors.forename: Cynthia
authors.initials: C
authors.lastname: Kwok
authors.forename: John
authors.initials: J
authors.lastname: Stanback
authors.forename: Josaphat K
authors.initials: JK
authors.lastname: Byamugisha
authors.forename: Tsungai
authors.initials: T
authors.lastname: Chipato
authors.forename: Thulani
authors.initials: T
authors.lastname: Magwali
authors.forename: Francis
authors.initials: F
authors.lastname: Mmiro
authors.forename: Sungwal
authors.initials: S
authors.lastname: Rugpao
authors.forename: Somchai
authors.initials: S
authors.lastname: Sriplienchan
authors.forename: Charles
authors.initials: C
authors.lastname: Morrison
mesh_terms: D000328:Adult; D015331:Cohort Studies; D003268:Contraception Behavior; D003271:Contraceptive Agents, Female / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular; D008525:Medroxyprogesterone / Q000008:administration & dosage*; D011247:Pregnancy; D018873:Pregnancy Rate; D011446:Prospective Studies; D013785:Thailand; D016896:Treatment Outcome; D014454:Uganda; D015030:Zimbabwe
chemical_list: D003271:Contraceptive Agents, Female; D008525:Medroxyprogesterone