RECENTLY PUBLISHED FINDINGS from several different studies have addressed the question of whether adolescent females who have sex with older partners have a greater risk of STD acquisition than their counterparts having sex with partners of relatively similar ages. 1–3 The research question is critically important, given that adolescent females commonly have sex with older male partners 4 and given the disproportionate STD burden experienced by this population. 5,6 However, published studies have not involved investigations of this research question among pregnant adolescent females, a potential high-risk population of adolescents 7 as well as a priority population for STD prevention. 8 Clearly, such studies are warranted, as an STD during pregnancy can be especially problematic, posing multiple risks to maternal and child health. 6,9,10
The primary purpose of this study was to compare unmarried pregnant African American adolescent females reporting sex with older partners to their counterparts reporting sex with similar-age male partners to determine whether the prevalence of STDs differed between the two groups. We also compared the two groups with regard to the frequency of unprotected vaginal sex (in past 30 days), adolescents’ self-efficacy in negotiating condom use, their frequency of sexual communications with their male sex partners, and their perceptions of whether their male sex partners were currently having sex with other women. We chose to study African American adolescents because of the disproportionately high rates of STDs in this population. 5,6,11,12 These pregnant African American adolescents were from low-income communities in a large Southern city.
Data for this study were obtained from the baseline measures collected during a pilot study of a randomized controlled trial designed to test an STD/HIV prevention program for pregnant African American female adolescents. Recruitment occurred in a prenatal clinic in Atlanta, Georgia.
During 1999 to 2000, 311 adolescent females aged 14 to 21 years were screened on their initial visit to the prenatal clinic to assess eligibility for study participation. Of these, 169 unmarried, pregnant, African American adolescent females met all the eligibility criteria and were enrolled in the study. Of those not eligible, most were not sexually active, could not plan to attend the intervention, or did not complete the entire baseline assessment protocol. The study protocol was approved by the institutional review board before implementation.
At study enrollment, adolescents completed a face-to-face interview administered by trained African American women, in their early twenties, in private examination rooms. The interview assessed the age of the adolescents’ male sex partner, frequency of unprotected vaginal sex (UVS) in the past 30 days, and whether the adolescents believed their partner was currently having sex with other women. Adolescents also completed a self-administered survey assessing their level of self-efficacy in negotiating condom use (four-item scale; α = 0.85) and their frequency of communication with sex partners about STD/HIV prevention, sex, and condom use (four-item scale; α = 0.86). Distributions for each measure were strongly skewed; therefore, we dichotomized each by performing a median split.
Finally, adolescents provided urine specimens that were evaluated for the presence of Neisseria gonorrhoeae, Chlamydia trachomatis, and Trichomonas vaginalis by means of nucleic acid amplification assays (ligase-chain reaction assays for N gonorrhoeae and C trachomatis and a polymerase chain reaction assay for T vaginalis). 13,14 Positive test results were defined according to criteria established by the manufacturer. Adolescents testing positive for STDs were notified and provided with prompt standard-of-care treatment.
Contingency table analyses (for dichotomous measures) and a t test (for the frequency measure of UVS) were conducted to assess bivariate associations between adolescents who reported their sex partners were at least 2 years older and those reporting similar-age partners. We chose this definition of “older” on the basis of previous research findings suggesting that a 2-year age difference may create substantial added risk for younger females. 2 To control for the potentially confounding influence of adolescents’ age, adolescents’ age was included as a covariate in subsequent logistic regression analyses for all variables achieving bivariate significance.
Characteristics of the Sample
Average age of the sample was 17.8 years (SD = 1.6 years). About two thirds (69.0%) were nulliparous. The majority (93.1%) reported that their current steady sex partner had conceived the pregnancy. The mean number of UVS acts in the past 30 days was 5.9 (SD = 11.2). Approximately one fifth (21.5%) of the adolescents tested positive for at least one of the three STDs assessed. Sixty-five percent of the adolescents (n = 109) reported that they had sex with male partners who were at least 2 years older.
Table 1 displays prevalence ratios, their 95% confidence intervals, and respective P values for each of the assessed measures (the exception is the prevalence of gonorrhea, as the number of cases detected [n = 2] was too low for meaningful analysis). As shown, adolescents with older partners were more than three times as likely to test positive for chlamydia as their counterparts reporting similar-age partners. Adolescents with older partners were also significantly more likely to report that their current sex partner was having sex with other women. None of the remaining bivariate comparisons displayed in Table 1 achieved significance.
The mean number of UVS acts among adolescents with older partners was 6.9, as compared with a mean of 4.1 among those reporting similar-age partners. Although this difference represents an effect size of 0.25, statistical significance was marginal (t = 2.0;P = 0.051).
In age-adjusted analyses, adolescents with older partners were four times more likely to test positive for chlamydia (adjusted OR = 4.03; 95% CI = 1.08–13.81;P = 0.04). Also, adolescents with older partners were about twice as likely to report that their sex partners were having sex with other women (adjusted OR = 2.22; 95% CI = 1.04–4.75;P = 0.04).
In contrast to the findings recently reported by Kissinger and colleagues, 1 the current study suggests that pregnant African American adolescents reporting sex with older partners may be at greater risk of chlamydia infection than their counterparts having sex with similar-age partners. We also found a statistical trend suggesting that pregnant adolescents with older partners may engage in UVS more frequently than those with similar-age partners (given a somewhat larger sample, the existing effect size would achieve statistical significance). No differences were observed between groups about possible antecedents of UVS, such as self-efficacy for condom negotiation and frequency of communication with partners about sex and STD/HIV prevention.
An important and unique finding of this study was that adolescents with older partners were more likely to report that their partner was having sex with other women. Thus, one potential explanation for the disproportionate prevalence of chlamydia among adolescents with older partners may be that their partners engage in greater levels of extrarelational sexual risk than do partners that more closely approximate adolescents’ own age. In essence, because older male partners may be more likely to have concurrent partners, they may pose additional risk of STD acquisition to members of their sexual network. Additionally, inflated STD risk for adolescent females may be a consequence of greater prevalence of chlamydia among men in their early twenties. 5
The findings are limited by several factors, including the inherent limitations of a cross-sectional study design and adolescents’ self-reports about their behaviors. The measure assessing whether adolescents believed their current partner was having sex with other women is also prone to misreport; however, whether differential misreporting occurred between groups is not known. Statistical power was also limited, as the study was not designed to detect small effect sizes. In addition, because distributions were skewed, median splits were used to dichotomize continuous variables; this procedure may have obscured potentially interesting information. Finally, the use of a convenience sample severely limits generalizability of the findings.
Further research is needed to corroborate these findings with other ethnic/racial groups of pregnant adolescents. Further research could also assess the positive predictive value of chlamydia screening among pregnant African American adolescents with older partners to determine the added utility of screening this potentially high-risk population.
Pregnant African American adolescent females with older partners may be particularly likely to test positive for chlamydia. Thus, in resource-constrained clinical settings, one implication of these findings is that pregnant adolescents with older partners may be a particularly vulnerable group and should be prioritized for targeted delivery of partner services. More frequent screening for chlamydia may also be cost-effective for pregnant adolescents with older partners.
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