title: Early adolescent pregnancy increases risk of incident HIV infection in the Eastern Cape, South Africa: a longitudinal study.
abstract: BACKGROUND
  Adolescents having unprotected heterosexual intercourse are at risk of HIV infection and unwanted pregnancy. However, there is little evidence to indicate whether pregnancy in early adolescence increases the risk of subsequent HIV infection. In this paper, we tested the hypothesis that adolescent pregnancy (aged 15 or younger) increases the risk of incident HIV infection in young South African women.
  
  
  METHODS
  We assessed 1099 HIV-negative women, aged 15-26 years, who were volunteer participants in a cluster-randomized, controlled HIV prevention trial in the predominantly rural Eastern Cape province of South Africa. All of these young women had at least one additional HIV test over two years of follow-up. Outcomes were HIV incidence rates per 100 person years and HIV incidence rate ratios (IRRs) estimated by Poisson multivariate models. Three pregnancy categories were created for the Poisson model: early adolescent pregnancy (a first pregnancy at age 15 years or younger); later adolescent pregnancy (a first pregnancy at age 16 to 19 years); and women who did not report an adolescent pregnancy. Models were adjusted for study design, age, education, time since first sexual experience, socio-economic status, childhood trauma and herpes simplex virus type 2 infection.
  
  
  RESULTS
  HIV incidence rates were 6.0 per 100 person years over two years of follow-up. The adjusted IRR was 3.02 (95% CI 1.50-6.09) for a pregnancy occurring at age 15 or younger. Women with pregnancies occurring between 16 and 19 years of age did not have a higher incidence of HIV (IRR 1.08; 95% CI 0.64-1.84). Early adolescent pregnancies were associated with higher partner numbers and a greater age difference with partners.
  
  
  CONCLUSIONS
  Early adolescent pregnancies increase the incidence of HIV among South African women. The higher risk is associated with sexual risk behaviours such as higher partner numbers and a greater age difference with partners rather than a biological explanation of hormonal changes during pregnancy.
authors.affiliation: School of Public Health, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa; nicola.chris@gmail.com.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Christofides
authors.affiliation: School of Public Health, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa; Gender & Health Research Unit, South African Medical Research Institute, Pretoria, South Africa.
authors.forename: Rachel K
authors.initials: RK
authors.lastname: Jewkes
authors.affiliation: Rollins School of Public Health, Emory University, Atlanta, GA, USA.
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Dunkle
authors.affiliation: Department of Psychology, University of Witwatersrand, Johannesburg, South Africa.
authors.forename: Mzikazi
authors.initials: M
authors.lastname: Nduna
authors.affiliation: School of Public Health, Faculty of Health Sciences, University of Witwatersrand, Johannesburg, South Africa; Gender & Health Research Unit, South African Medical Research Institute, Pretoria, South Africa.
authors.forename: Nwabisa Jama
authors.initials: NJ
authors.lastname: Shai
authors.affiliation: Rollins School of Public Health, Emory University, Atlanta, GA, USA.
authors.forename: Claire
authors.initials: C
authors.lastname: Sterk
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D005260:Female; D015658:HIV Infections / Q000453:epidemiology*; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000453:epidemiology*; D011253:Pregnancy in Adolescence / Q000706:statistics & numerical data; D012307:Risk Factors; D012725:Sexual Behavior / Q000706:statistics & numerical data; D013019:South Africa / Q000453:epidemiology; D055815:Young Adult
keywords: HIV/AIDS; South Africa; adolescent pregnancy; longitudinal data; sexual risk behaviour