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Telling truth from Ys: an evaluation of whether the accuracy of self-reported semen exposure assessed by a semen Y-chromosome biomarker predicts pregnancy in a longitudinal cohort study of pregnancy
  1. Janet E Rosenbaum1,
  2. Jonathan Zenilman2,
  3. Johan Melendez2,
  4. Eve Rose3,
  5. Gina Wingood3,
  6. Ralph DiClemente3
  1. 1Department of Epidemiology and Biostatistics, School of Public Health, SUNY Downstate Medical Center, Brooklyn, New York, USA
  2. 2Department of Infectious Diseases, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
  3. 3Behavioral Sciences and Health Education, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
  1. Correspondence to Janet E Rosenbaum, Department of Epidemiology and Biostatistics, School of Public Health, SUNY Downstate Medical Center, Brooklyn, 450 Clarkson Ave, Mailstop 43, Brooklyn, NY 11203, USA; janet{at}


Objectives Adolescents may use condoms inconsistently or incorrectly, or may over-report condom use. This study used a semen exposure biomarker to evaluate the accuracy of female adolescents’ reports of condom use and predict subsequent pregnancy.

Methods The sample comprised 715 sexually active African-American female adolescents, ages 15–21 years. At baseline, 6 months and 12 months, participants completed a 40-min interview and were tested for semen Y-chromosome with PCR from a self-administered vaginal swab. We predicted pregnancy from semen exposure under-report using multivariate regression controlling for oral contraception, reported condom use and coital frequency.

Results At the 3 surveys, 30%, 20% and 15% of adolescents who reported always using condoms tested positive for semen exposure. At 6 month follow-up, 20.4% and 16.2% of the adolescents who under-reported semen exposure reported pregnancy, a higher pregnancy rate than accurate reporters of semen exposure, even accurate reporters who reported never using condoms (14.2% and 11.8%). Under-reporters of semen exposure were 3.23 (95% CI (1.61, 6.45)) times as likely to become pregnant at 6-month follow-up and 2.21 (0.94, 5.20) times as likely to become pregnant at 12-month follow-up as accurate reporters who reported not using contraception, adjusting for self-reported coital frequency.

Conclusions Adolescents who under-report semen exposure may be at uniquely high risk for unplanned pregnancy and STIs, and may also under-report coital frequency. Condom efficacy trials that rely on self-report may yield inaccurate results. Adapted to a clinical setting, the Y-chromosome PCR could alert women to incorrect or inconsistent condom use.

  • Adolescent
  • Contraception
  • Pregnancy
  • DNA Amplification
  • Condoms

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