Objective
To examine whether sexual orientation is associated with disparities in teen pregnancy and hormonal contraception use among adolescent females in 2 intergenerational cohorts.
Study Design
Data were collected from 91,003 women in the Nurses’ Health Study II (NHSII), born between 1947-1964, and 6463 of their children, born between 1982-1987, enrolled in the Growing Up Today Study (GUTS). Log-binomial models were used to estimate risk ratios for teen pregnancy and hormonal contraception use in sexual minorities compared with heterosexuals and metaanalysis techniques were used to compare the 2 cohorts.
Results
Overall, teen hormonal contraception use was lower and teen pregnancy was higher in NHSII than GUTS. In both cohorts, lesbians were less likely, whereas the other sexual minorities were more likely, to use hormonal contraception as teenagers compared with their heterosexual peers. All sexual minority groups in both cohorts, except NHSII lesbians, were at significantly increased risk for teen pregnancy, with risk ratios ranging from 1.61 (95% confidence interval, 0.40–6.55) to 5.82 (95% confidence interval, 2.89–11.73). Having an NHSII mother who was pregnant as a teen was not associated with teen pregnancy in GUTS participants. Finally, significant heterogeneity was found between the 2 cohorts.
Conclusion
Adolescent sexual minorities have been, and continue to be, at increased risk for pregnancy. Public health and clinical efforts are needed to address teen pregnancy in this population.
Regardless of intention, teen pregnancy is associated with numerous adverse health and social outcomes. Compared with women who give birth in their 20s, teens are more likely to experience a quicker repeat pregnancy, more unemployment, poverty, and welfare reliance, and single parenthood. Infants of teen mothers are more likely to be premature and die before the age of 1 year. Compared with children of older mothers, these children also do more poorly on indicators of health and social wellbeing.
Although research examining pregnancy rates by sexual orientation is sparse, prior studies suggest that sexual minority females (eg, bisexuals, lesbians) may be at heightened risk compared with heterosexual peers. Risk factors for teen pregnancy, such as earlier sexual initiation and more sexual partners, are more common in female sexual minorities who report a high proportion of male sexual contacts, a younger age of sexual initiation, and more partners (male or female) compared with heterosexuals. Sexual minority females at risk for unintended pregnancy may also be less likely than heterosexual females to use contraceptives, and, in particular, highly effective hormonal contraceptives. One study found that this group underutilizes regular reproductive health screenings such as Papanicolaou smears and sexually transmitted infection (STI) tests, in which contraceptive counseling is offered. In addition, sexual minority adolescent females may have additional risk factors such as engaging in risky sexual behavior with men, to hide their sexual orientation.
Sex education, contraceptive technology, and attitudes about sexual orientation have changed over time and have affected historic trends in teen pregnancy and contraceptive use. For example, comprehensive sex education has been shown to reduce teen pregnancy compared with no education or abstinence-only education. In addition, an estimated 60% of sexually active teens report using a highly effective form of contraception (eg, intrauterine devices and hormonal methods) in 2010, which is an increase from 47% in 1995. Contraception is less stigmatized than it was even 1 generation ago and physicians are more likely to raise the issue with patients. Although initial research has been conducted on teen pregnancy among sexual minorities, these studies were of limited power, combined sexual minority groups, and were restricted to a single generation.
Using data from 2 intergenerational longitudinal cohort studies in which participants were teenagers during different periods (Nurses’ Health Study II [NHSII] 1969-1983 and Growing Up Today Study [GUTS] 1995-2006), we examined sexual orientation group disparities in teen hormonal contraception use and pregnancy. We explored 3 aims: (1) sexual minority disparities; (2) intergenerational effects; and (3) historic cohort differences. First, we examined whether there were sexual orientation disparities in teen hormonal contraception and pregnancy. Next, we focused on the effect of having a mother with a teen pregnancy on her daughter’s risk of teen pregnancy. Thirdly, we formally tested for differences between the 2 generations. For aim 1, we hypothesized that compared with completely heterosexual females, sexual minorities would be less likely to use hormonal contraception as teens in both cohorts. We also hypothesized sexual minority teenagers would have higher risks of becoming pregnant before age 20 in both the NHSII and GUTS cohorts. For aim 2, we expected having a mother with a teen pregnancy would be associated with her daughter’s teen pregnancy risk. Finally for aim 3, we hypothesized that all of the disparities would vary historically and be more pronounced among the NHS cohort compared with the GUTS cohort.
Methods
Study sample
NHSII is a longitudinal cohort that began in 1989, enrolling 116,678 female nurses from 14 US states. Participants were between 25 and 42 years of age at baseline and born between 1947 and 1964. This cohort has been, and continues to be, followed with the use of biennial mailed questionnaires to update information on health-related behavior and to determine incident disease outcomes. In 1996, the NHSII women provided consent and contact information for their children between the ages of 9 and 14 years, born between 1982 and 1987, thereby creating another longitudinal cohort known as the GUTS. Questionnaires were mailed to more than 25,000 of these children; 9039 girls (68%) and 7843 (58%) boys returned completed questionnaires, indicating their consent. When NHSII or GUTS participants failed to respond to the first few mailings, extensive follow-up procedures were implemented to ensure a high response rate. More detailed information on recruitment and study protocols are available elsewhere. We limited the current analysis to female NHSII and GUTS participants who reported their sexual orientation, age, race, and geographic region (n = 88,398). This study was approved by the Brigham and Women’s Hospital institutional review board.
Measures
Sexual orientation
In 1995, the following question was added to the long form of the NHSII questionnaire, after being pilot tested: “Whether you are currently sexually active, what is your sexual orientation or identity? (Please choose one answer). (1) Heterosexual, (2) Lesbian, gay, or homosexual, (3) Bisexual, (4) None of these, (5) Prefer not to answer.” For ease of interpretation, analyses did not include participants who responded with “None of these” or “Prefer not to answer” (1%, n = 616).
Sexual orientation is measured in GUTS with a question adapted from the Minnesota Adolescent Health Survey asking about identity and feelings of attraction: “Which of the following best describes your feelings? (1) Completely heterosexual (attracted to persons of the opposite sex), (2) Mostly heterosexual, (3) Bisexual (equally attracted to men and women), (4) Mostly homosexual, (5) Completely homosexual (gay/lesbian, attracted to persons of the same sex), (6) Not sure.” We collapsed the “mostly heterosexual” and “bisexual” groups to form 1 category, because preliminary analyses showed that associations with predictors and outcomes were similar in the 2 groups and combining them increased statistical power. Similarly, the “mostly homosexual” and “completely homosexual” responses were combined to form a lesbian category. Again, analyses did not include participants who were unsure (n = 6) or missing (n = 14) the orientation item response. In addition, the sex of participants’ sexual contacts was measured with an item reading: “During your life, the person(s) with whom you have had sexual contact is (are)…” Responses included “I have not had sexual contact with anyone,” “Females,” “Males,” or “Female(s) and Male(s).” An indicator variable was used for missing data on the sex of sexual contacts (n = 33). An individual could therefore endorse being a sexual minority through their identity/attractions in the first question above and/or through their behavior in the next question.
This analysis used the most recently available data in NHSII from 1995 to categorize the following sexual orientation groups for that cohort as: “heterosexual,” “bisexual,” or “lesbian, gay, or homosexual.” The most recently available GUTS data from 2007 were used to categorize that cohort into the following groups: “completely heterosexual” with no same-sex partners, “completely heterosexual” with same-sex partners, “mostly heterosexual/bisexual,” or “mostly homosexual/completely homosexual.”
Teen hormonal contraceptive use
NHSII participants reported their history of using oral contraceptives on the 1989 baseline questionnaire. Beginning in 1999, each GUTS questionnaire has included various questions about oral contraceptives as well as more newly available hormonal contraceptives ( Supplementary Table ; Appendix ). We categorized participants as a teen hormonal contraception user if they reported any such use before age 20 ( Figure 1 ).
Teen pregnancy
Similarly, NHSII participants reported their pregnancy histories on the 1989 baseline questionnaire. Beginning in 1999, each GUTS questionnaire included questions about pregnancy ( Supplementary Table ; Appendix ). We defined teen pregnancy as occurring before the age of 20. Using this definition enabled comparisons between our findings and the previous literature on teen pregnancy, including among sexual minorities ( Figure 2 ).
Covariates
Additional covariates included age, race, and geographic region based on a priori knowledge and available data in both cohorts. Age and racial information were collected on both baseline cohort questionnaires in 1989 for NHSII and 1996 for GUTS. Geographic region was accessed in NHSII from an item on the 1993 questionnaire that read: “In which state did you live at age 15?” GUTS geographic region was collected on each questionnaire, so we assigned the region at which each participant indicated they lived at age 15. Analyses did not include participants who did not report their race (n = 1798; 1.5% in NHSII and n = 26; 0.4% in GUTS) or geographic region (n = 2007; 2.1% in NHSII). GUTS participants who reported living outside of the United States at age 15 were also excluded due to small sample size (n = 11).
Statistical analysis
Descriptive statistics and multivariable regression analyses were conducted using SAS statistic software 9.2 (SAS Institute, Cary, NC). All analyses were cross-sectional with heterosexual females in NHSII and completely heterosexual females with no same-sex partners in GUTS as the reference groups. Log-binomial models were used to estimate risk ratios (RRs) and 95% confidence intervals (CIs) for the outcomes of teen hormonal contraceptive use and pregnancy. When the models did not converge, log-Poisson models were used, which provide consistent but not fully efficient estimates of the RR and its 95% CI. Generalized estimating equations (GEE) were used to account for sibling clusters in GUTS.
Additional analyses were conducted to examine the effect of having a NHSII mother who was pregnant as a teen on the risk of having a pregnancy before age 20 years among GUTS participants. Finally, the 2 cohorts were compared on both outcomes using metaanalysis techniques to examine heterogeneity. Statistical tests for between-study heterogeneity were the χ 2 test for heterogenity (Cochran Q-statistic) and the I 2 statistic, which estimates the proportion of total variance because of between-study variability.
Results
Among the 81,974 NHSII participants included in the analyses, 99% described themselves as heterosexual, <1% as bisexual, and 1% as lesbian. Among the 6424 GUTS female participants included in the analyses, 84% described themselves as completely heterosexual, 1% as completely heterosexual with same-sex partners, 14% as mostly heterosexual/bisexual, and 1% as lesbian. Table 1 displays further characteristics of the 2 cohorts by sexual orientation. Teen hormonal contraception use was reported by 34% of NHSII women and 69% of GUTS participants, although 10% of NHSII women (mean age, 18.0 years) and 2% of GUTS participants (mean age, 17.9 years) reported a teen pregnancy.
| Cohort | Heterosexual (n = 81,053) | Bisexual (n = 283) | P value b | Lesbian (n = 638) | P value b |
|---|---|---|---|---|---|
| NHSII (n = 81,974) | |||||
| Mean baseline age, years (SD) (range, 24–44 y) | 34.5 (4.7) | 35.2 (4.4) | .01 | 35.3 (4.6) | < .0001 |
| White race, % (n) c | 94.2 (76,372) | 94.4 (267) | .93 | 96.9 (618) | .003 |
| Geographic region at age 15, % (n) c | |||||
| Midwest | 36.5 (29,547) | 26.5 (75) | 27.6 (176) | ||
| West | 10.8 (8769) | 12.7 (36) | 15.7 (100) | ||
| South | 13.4 (10,887) | 13.4 (38) | 15.7 (100) | ||
| Northeast | 37.3 (30,253) | 44.5 (126) | 38.2 (244) | ||
| International | 2.0 (1597) | 2.8 (8) | < .0001 | 2.8 (18) | .001 |
| Hormonal contraceptive use <20 y old, % (n) | 34.4 (27,870) | 44.2 (125) | < .0001 | 28.8 (184) | .003 |
| Pregnancy <20 y old, % (n) | 9.9 (7882) | 20.4 (56) | < .0001 | 7.2 (44) | .02 |
| Completely heterosexual (n = 5368) | Completely heterosexual with same-sex partners (n = 91) | P value b | Mostly heterosexual/bisexual (n = 891) | P value b | Lesbian (n = 74) | P value b | |
|---|---|---|---|---|---|---|---|
| GUTS (n = 6424) | |||||||
| Mean baseline age, years (SD) (range, 9–15) | 11.5 (1.6) | 12.2 (1.5) | < .0001 | 11.7 (1.6) | .0006 | 12.0 (1.6) | .004 |
| White race, % (n) | 94.1 (5052) | 96.7 (88) | .20 | 90.0 (802) | < .0001 | 91.9 (68) | .70 |
| Geographic region at age 15, % (n) | |||||||
| Midwest | 36.6 (1967) | 35.2 (32) | 30.4 (271) | 23.0 (17) | |||
| West | 13.7 (734) | 13.2 (12) | 19.6 (175) | 10.8 (8) | |||
| South | 14.8 (792) | 16.5 (15) | 11.5 (102) | 21.6 (16) | |||
| Northeast | 34.9 (1875) | 35.2 (32) | .39 | 38.5 (343) | .37 | 44.6 (33) | .62 |
| Hormonal contraceptive use <20 y old, % (n) | 67.8 (3535) | 88.6 (78) | < .0001 | 79.4 (681) | < .0001 | 50.0 (34) | .004 |
| Pregnancy <20 y old, % (n) | 1.8 (95) | 8.8 (8) | .02 | 3.9 (35) | .001 | 2.7 (2) | .64 |
| NHSII mother had teen pregnancy, % (n) | 7.1 (356) | 12.6 (11) | .04 | 9.0 (76) | .06 | 5.9 (4) | .68 |
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