title: Pregnancy rates in HIV-positive women using contraceptives and efavirenz-based or nevirapine-based antiretroviral therapy in Kenya: a retrospective cohort study.
abstract: BACKGROUND
  Concerns have been raised about efavirenz reducing the effectiveness of contraceptive implants. We aimed to establish whether pregnancy rates differ between HIV-positive women who use various contraceptive methods and either efavirenz-based or nevirapine-based antiretroviral therapy (ART) regimens.
  
  
  METHODS
  We did this retrospective cohort study of HIV-positive women aged 15-45 years enrolled in 19 HIV care facilities supported by Family AIDS Care and Education Services in western Kenya between Jan 1, 2011, and Dec 31, 2013. Our primary outcome was incident pregnancy diagnosed clinically. The primary exposure was a combination of contraceptive method and efavirenz-based or nevirapine-based ART regimen. We used Poisson models, adjusting for repeated measures, and demographic, behavioural, and clinical factors, to compare pregnancy rates among women receiving different contraceptive and ART combinations.
  
  
  RESULTS
  24,560 women contributed 37,635 years of follow-up with 3337 incident pregnancies. In women using implants, adjusted pregnancy incidence was 1.1 per 100 person-years (95% CI 0.72-1.5) for nevirapine-based ART users and 3.3 per 100 person-years (1.8-4.8) for efavirenz-based ART users (adjusted incidence rate ratio [IRR] 3.0, 95% CI 1.3-4.6). In women using depot medroxyprogesterone acetate, adjusted pregnancy incidence was 4.5 per 100 person-years (95% CI 3.7-5.2) for nevirapine-based ART users and 5.4 per 100 person-years (4.0-6.8) for efavirenz-based ART users (adjusted IRR 1.2, 95% CI 0.91-1.5). Women using other contraceptive methods, except for intrauterine devices and permanent methods, had 3.1-4.1 higher rates of pregnancy than did those using implants, with 1.6-2.8 higher rates in women using efavirenz-based ART.
  
  
  CONCLUSIONS
  Although HIV-positive women using implants and efavirenz-based ART had a three-times higher risk of contraceptive failure than did those using nevirapine-based ART, these women still had lower contraceptive failure rates than did those receiving all other contraceptive methods except for intrauterine devices and permanent methods. Guidelines for contraceptive and ART combinations should balance the failure rates for each contraceptive method and ART regimen combination against the high effectiveness of implants.
  
  
  BACKGROUND
  None.
authors.affiliation: Division of Infectious Diseases, University of California, San Francisco, San Francisco, CA, USA. Electronic address: rcpatel@uw.edu.
authors.forename: Rena C
authors.initials: RC
authors.lastname: Patel
authors.affiliation: Research, Care and Training Program, Centre for Microbiology Research, Kenya Medical Research Institute, Kisumu, Kenya.
authors.forename: Maricianah
authors.initials: M
authors.lastname: Onono
authors.affiliation: Division of HIV/AIDS, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Monica
authors.initials: M
authors.lastname: Gandhi
authors.affiliation: Bixby Center for Global Reproductive Health, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Cinthia
authors.initials: C
authors.lastname: Blat
authors.affiliation: School of Medicine, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Jill
authors.initials: J
authors.lastname: Hagey
authors.affiliation: Center for AIDS Prevention Studies, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Starley B
authors.initials: SB
authors.lastname: Shade
authors.affiliation: Department of Medicine, and Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Eric
authors.initials: E
authors.lastname: Vittinghoff
authors.affiliation: Research, Care and Training Program, Centre for Microbiology Research, Kenya Medical Research Institute, Kisumu, Kenya.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Bukusi
authors.affiliation: Bixby Center for Global Reproductive Health, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Newmann
authors.affiliation: Bixby Center for Global Reproductive Health, Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, San Francisco, CA, USA.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Cohen
mesh_terms: D000293:Adolescent; D000328:Adult; D000480:Alkynes; D019380:Anti-HIV Agents / Q000008:administration & dosage*; D048588:Benzoxazines / Q000008:administration & dosage*; D003270:Contraceptive Agents / Q000008:administration & dosage*; D003521:Cyclopropanes; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000453:epidemiology; D006801:Humans; D007630:Kenya / Q000453:epidemiology; D008137:Longitudinal Studies; D019829:Nevirapine / Q000008:administration & dosage*; D011247:Pregnancy; D018873:Pregnancy Rate / Q000639:trends; D012189:Retrospective Studies; D016896:Treatment Outcome
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003270:Contraceptive Agents; D003521:Cyclopropanes; D019829:Nevirapine; C098320:efavirenz