e Teen STAR (Sexuality Teaching in the context of Adult Re-
sponsibility) program avoids the two extremes of sexuality edu-
cation—abstinence-only or “comprehensive”—as it balances the
facts of fertility with the emotional, cognitive, social, and spiritual
aspects of human sexuality.
A primary and secondary program was initiated to prevent sexual
activity among Chilean teens aged 12–18 years old. Among the
females who participated in the program, only 3.4% transitioned
from virginity to intercourse, compared with 12.4% of control
females who did not participate in the program. Among the males
who participated in the program, only 8.8% transitioned from
virginity to intercourse, compared with 17.6% of control males
who did not participate in the program. Twenty-one percent of
sexually active program subjects discontinued intercourse, com-
pared with 9% controls. Of those program subjects who discon-
tinued intercourse, none resumed activity at the end of one year,
whereas 11.7% of control subjects did resume sexual activity.
Pregnancy rates were studied among female students who partici-
pated in Teen STAR versus female students who did not partici-
pate in the program (i.e., the control group). Average pregnancy
rates per year were 0.87% in the program group and 4.87% in the
control group during the follow-up period.
During the last twenty-ﬁve years, there have been extensive
eﬀorts to reduce the consequences of risky adolescent sex-
ual behaviors by programs classiﬁed either as abstinence-
only or as comprehensive sexuality (also known as abstinence-based
education, safer-sex, secular, or abstinence-plus programs) education
programs (omas 2000, Silva 2002). e ﬁrst kind of program—
170 Human Fertility: Where Faith & Science Meet
abstinence-only sex education programs, which the United States
government deﬁned under Section 510 of the 1996 Social Security
Act—can be perceived as inherently coercive in the sense that they
do not promote free choice on the part of the teen participant. ey
can also be seen as authoritarian in approach. e second kind of
program—comprehensive sexuality education—also promotes ab-
stinence as the ﬁrst and best choice for preventing pregnancy and
sexually transmitted diseases (STDs), including Human Immunode-
ﬁciency Virus (HIV), but it also provides education and sometimes
services regarding all contraceptive methods. ese comprehensive
sexuality education programs are designed to assist students in be-
coming well-informed decision makers (Pittman 2006), but these
programs sometimes view the consequences of sexual behaviors
mechanistically, or isolated from social and individual values.
Although controlled randomized evaluation has been scant for
both approaches (Silva 2002), the available evidence suggests that
adolescent sexual behavior is a complex phenomenon and that ad-
dressing it requires an integrated, sophisticated approach that is not
unduly bound by ideological simplicity (Kirby 2001).
e Teen STAR (Sexuality Teaching in the context of Adult Re-
sponsibility; see: www.teenstar.cl and www.teenstarprogram.org.)
program began twenty-seven years ago in an attempt to oﬀer a pro-
gram of education in human sexuality that encompasses the whole
person. In so doing, the program has avoided the two extremes of
abstinence-only and comprehensive sexuality education programs.
Teen STAR is an interactive, holistic education program in hu-
man sexuality leading to the acceptance of one’s own sexuality and
fertility. It involves feelings as well as intellect, requires that fertility
patterns be learned through observation, and demands both parental
participation and teacher-student conﬁdentiality. Learning through
observation challenges teens to integrate their biological capacity to
be fathers or mothers into all aspects of their lives, i.e., social, emo-
tional, intellectual, spiritual, and physical aspects of their sexuality
(Vigil 2004a; de Malherbe 2005). Adolescence can produce a tem-
porary “deafness” to the teachings that adults would like to transmit
to young people (Hall et al. 2004). Teens need to make decisions
about their own behavior, make their own discoveries, and reach
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 171
their own conclusions. Adolescents are immersed in the task of es-
tablishing their own ego identity. is requires at least a theoretical
distancing from the “parental ego”. Knowledge of their fertility helps
them understand their sexuality (Vigil et al. 2006a, 2006b), as well as
their capacity to procreate. Experiencing their body’s messages about
fertility and its potential for procreation is a source of intellectual
learning for teens. Additionally, it allows teens to choose to express
this potential with total freedom and to save it for a committed re-
lationship: marriage (Vigil et al. 2002a). At the same time, parental
involvement is still an important component of the Teen STAR pro-
gram. Other studies have also shown that parental participation in
interventions appears to be associated with a higher tendency toward
abstinence (Silva 2002).
To reach these goals, Teen STAR develops the following areas:
1. Improving self-identity and self-esteem. Adolescents need to
know who they are, so they are encouraged to become aware of
themselves as free, if limited, persons.
2. Valuing their freedom and decision-making ability. Teens are
informed about free and responsible choices. Self-control is a
prized fruit that feeds on self-knowledge.
3. Building a feeling of respect for the gift of life. Human life is a
gift, received to be given. Only those teens who value their own
life will be able to present it as a gift to others. If youngsters de-
spise themselves, they will despise life and will not consider their
possible surrender as a precious gift.
e objective of the present review is to analyze the results obtained
with the Teen STAR program in two randomized, controlled tri-
als: (1) a study conducted to evaluate the eﬀect of Teen STAR on
sexual behaviour among Chilean female and male adolescents (Vigil
et al. 2005a) and (2) a study conducted to evaluate the eﬀect of Teen
STAR on teenage pregnancy rates in Chilean adolescent girls (Ca-
bezón et al. 2005).
172 Human Fertility: Where Faith & Science Meet
Teachers from diﬀerent schools voluntarily participating in the study
were trained in a ﬁve-day seminar-workshop at the Pontiﬁcal Catho-
lic University of Chile (PUC), Santiago. ey were prepared to de-
velop all units of the Teen STAR program with the students and hold
eﬀective meetings with parents. Teen STAR has diﬀerent develop-
mental curricula, diﬀerentiated on the basis of age, sex, and school
class. Each curriculum has 14 units (Cabezón et al. 2005):
1. Initial session and introduction to the program
2. Diﬀerences between genders
3. Identiﬁcation of prejudices on female and male’s features
4. Anatomy and physiology of human reproductive system
5. Puberty, fertility in women, and fertility in men
6. Fertility awareness, registration of fertility records (classes dis-
tributed along the course)
7. Knowing emotions and controlling behaviors
8. e manipulation of sexuality in media
9. Self-assurance and maintaining decisions
10. Marriage, family, and parenthood
11. Beginning of life, value of human life
12. Family planning methods, contraception
13. Pregnancy, delivery, breastfeeding
14. Final session and feedback
e units are delivered in one or more 45–90 minute sessions. Pro-
gression depends on satisfactory completion of each unit by the stu-
dents before passing to the next unit.
Teachers were trained to maintain ﬂuent communication with par-
ents, while at the same time respecting the conﬁdentiality of com-
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 173
munications with students. Personal interviews with the students are
an integral aspect of the program, so teachers were also trained in
counseling skills. Each teacher received a Teen STAR manual includ-
ing the curricula and supplementary articles and audiovisual materi-
als, such as posters, videotapes, and CDs.
e study on Teen STAR’s eﬀect on adolescent sexual behavior (Vigil
et al. 2005a; 2005b) included 740 Chilean white teens (12–18 years
old) attending 10 basic schools or high schools (Figure 1). e study
and control groups consisted of students in the same grade in classes
Figure 1: Flow of Participants through Each Stage of the Study of the
Eﬀect of Teen STAR on Adolescent Sexual Behavior
174 Human Fertility: Where Faith & Science Meet
of 30 to 40 students. ey were randomly divided into program and
control groups by drawing the letter of the class from a black bag.
e program group (n = 147 females, 251 males) consisted of those
teens who participated in the Teen STAR program with parental con-
sent. A trained Teen STAR teacher who was part of the school’s staﬀ
and had voluntarily agreed to participate in the training workshop
worked with the program group over eight months. e program’s
curricula, diﬀerentiated on the basis of age, sex, and school class,
were oﬀered twice a week during school hours. In addition, at least
one personal interview was conducted with each student as part of
the program. e intervention with parents consisted of three meet-
ings along the school year, which described the characteristics of the
program and physical and psychological development of teens and
requested parents’ feedback. Program impact was assessed by means
of anonymous pre- and post-program questionnaires administered
to study and control subjects (Vigil et al. 2005a).
e control group (n = 147 females, 195 males) comprised stu-
dents with similar characteristics (same age, sex, and socioeconomic
and educational levels) from parallel classes at each school who did
not participate in the Teen STAR program and received the regular
school education. ese students also completed the pre- and post-
program questionnaires. Questionnaires were given at the same time
to control and program students. e questionnaires for both groups
were identiﬁed by a name chosen by each student and known only to
him or her. e completed questionnaires were placed into a special
box, which was sealed in front of the students. e box was then sub-
mitted to a statistician. e pre- and post-program responses of the
control group and the program group were compared. e surveys
contained 135 questions about diverse topics. eir analysis allowed
evaluation of the impact of the Teen STAR program on the teens’
sexual activity via rates for (1) primary abstinence, (2) discontinua-
tion of intercourse, (3) resumption of sexual activity, and (4) inﬂu-
ence of the curriculum on abstinence (Vigil et al. 2005a).
e study was approved by the directing councils of all participat-
ing educational establishments, as well as by the Ethics Committee
of the Faculty of Biological Sciences of the Pontiﬁcal Catholic Uni-
versity of Chile, Santiago.
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 175
e study included all those teenagers willing to take part who had
their parents’ consent. Before the initiation of the study, all adoles-
cents younger than 12 and older than 18 years of age (both ends of
the normal distribution curve) were excluded. Also excluded from
the outcome analysis were all those students whose pre- and post-
tests either were missing identiﬁers (e.g., missing date of birth) or
had internal inconsistencies or unreliable data, (e.g., noncorrelated
questionnaires in terms of date of birth and ID code, omitted ques-
tions, or noncorrelated answers to paired questions in the question-
naire). For certain variables, exclusion criteria were lack of answer or
dissenting replies (e.g., saying he/she had intercourse in pre-program
questionnaire and saying he had not in post-program questionnaire)
to a speciﬁc question (Vigil et al. 2005a).
e statistical study employed a student’s t-test and analysis for
sample homogeneity for dropouts in both groups.
A randomized, controlled study to evaluate the eﬃcacy of the pro-
gram in preventing adolescent pregnancy (Cabezón et al. 2005) was
conducted that compared intervention with the Teen STAR program
with no intervention in a public girls school in San Bernardo, a pe-
ripheral community of Santiago, Chile. e trial included a total of
1,259 Chilean white girls, 15 to 16 years old at the time they joined
the study, who were divided into three cohorts depending on what
year they started high school: the 1996 cohort of 425 students, in
which no one received intervention; the 1997 cohort, in which 210
students received Teen STAR and 213 (control group) did not; and
the 1998 cohort, in which 328 students received Teen STAR and 83
(control group) did not (Cabezón et al. 2005; Rev. Pan. 2005) (Fig-
ure 2 [next page]). As in the previous study, participants were ran-
domly divided into program and control groups by drawing the let-
ter of the class from a black bag. e classes each had 30 to 35 girls.
e 1998 cohort included more girls in the program group. is
was because initial results obtained with the 1997 cohort showed a
decrease in pregnancy rates, so we were asked to expand the program
group. Eight teachers were available, so the program group included
eight classes (328 girls) for the 1998 cohort. All cohorts were fol-
176 Human Fertility: Where Faith & Science Meet
lowed for four years; pregnancy rates were recorded for program and
control groups. Pregnancy rates were measured, and risk ratio (RR)
with 95% conﬁdence interval (CI) was calculated for program and
control groups in each cohort. e homogeneity test consisted of the
application of the chi-square (χ2) test (Cabezón et al. 2005).
In the program group, 8.8% of virgin males and 3.4% of virgin fe-
males transitioned to sexual activity, versus 17.6% of virgin males
and 12.4% of virgin females in the control group (p = 0.004) (Vigil
et al. 2005a; 2005b) (see Figure 3 [next page]). e delay observed in
the initiation of sexual activity within the program group was simi-
lar for females and males (V-square = 0.32; p = 0.571; V-square is a
corrected χ2 value obtained from a 2 x 2 table) (Cortés et al. 2006).
Within the group of sexually active students, 20.5% of program
students discontinued sexual activity (i.e., had no act of intercourse
within the ﬁnal three months), compared with 9% of students in the
Figure 2: Flow of Participants rough Each Stage of the Study of the
Eﬀect of Teen STAR on Teenage Pregnancy Prevention
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 177
control group who discontinued sexual activity (p ≤ 0.03). Among
students who had initiated sexual activity before the intervention,
but who were sexually inactive at the time the study began, 11.7%
of the control group resumed intercourse during the period of the
study, while none of the students in the program group did (Vigil
et al. 2005a). Adolescents participating in the program exhibited
an increase in the number of reasons for not having intercourse, or
“maintaining abstinence,” from one reason at the beginning of the
program to three reasons at the end of it (Vigil et al. 2005a).
Over the four-year follow-up, 6 pregnancies occurred in the program
group and 35 in the control group. Average pregnancy rates per year
were 0.87% for the program and 4.87% for the control group dur-
ing the follow-up period. For the 1996 cohort (no intervention), the
pregnancy rate was 14.7%. For the 1997 cohort, the pregnancy rates
were 3.3% and 18.91% for program and control groups, respec-
virgin to non-virgin transition (%)
Control males Program males Control females Program females
Figure 3: Transition Rates of Sexual Activity in Program and
Control Students for Males and Females
178 Human Fertility: Where Faith & Science Meet
tively (RR: 0.17619, CI: 0.0759–0.4086). For the 1998 cohort, the
pregnancy rates were 4.43% and 22.66% for program and control
groups, respectively (RR: 0.19574, CI: 0.0995–0.3848) (Cabezón
et al. 2005; Rev. Pan. 2005) (see Figure 4). Program adolescents also
exhibited a signiﬁcant change in their reasons for abstinence, partic-
ularly “I can’t seem to ﬁnd the right person” and “I don’t feel ready,”
suggesting an internalization of their locus of control. ey pointed
out that they felt less prepared to have sexual intercourse. A reverse
trend was found in the control group adolescents for the second of
the above reasons (being one year older, they felt better qualiﬁed to
initiate sexual activity), while choices for the ﬁrst reason remained
unchanged (Cabezón et al. 2005).
Although many sex education programs have been conducted and
lavish amounts of money have been spent, it is well known that
teenage pregnancies continue to be a signiﬁcant problem. In Chile,
Figure 4: Overall Cumulative Pregnancy Rates over 4-Year Follow-Up
for the 1997 and 1998 Cohorts
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 179
15.6% of all live births in the 1996–1998 period involved moth-
ers younger than 20 years. erefore, in Chile, about 40,000 teens
become mothers every year (Vigil et al. 2005a), and this does not
consider illegal abortions or pregnancies starting at 19 and ending at
20 years (Álvarez et al. 1990; Delpiano and Aguilera Reyes. 2001).
In countries such as the United States, teenage pregnancies have
decreased during the last 15 years, but still about 800,000 adoles-
cents give birth each year. It should be noted that the decrease in
teenage pregnancy rates is diﬀerent according to ethnic groups. Cur-
rently, the highest pregnancy rates are within the Hispanic groups
Adolescents are at high risk of contracting STDs: nearly one half
of new reported cases occur among 15 to 24 year old people (Brindis
2006). Teens’ perceptions of invulnerability (Hall et al. 2004), teen
pregnancies, and the increasingly earlier initiation of sexual activity
signal an urgent need to provide eﬀective sex education programs to
this age group.
DiCenso’s meta-analysis (DiCenso et al. 2002) of primary pre-
vention strategies found that provision of contraception, even while
acknowledging that abstinence is preferable, did not delay the ini-
tiation of sexual intercourse or improve use of birth control among
young men and women. Nor was there a reduction in pregnancies
among young women, while the interventions increased pregnancies
in partners of male participants.
Other studies, in addition to ours, have demonstrated that sexual
education programs can have an impact in the delay of initiation of
sexual activity and teen pregnancies (Olsen et al. 1991; Darroch et
al. 2000; Sather and Zinn 2002; Rev. Pan. 2005). ese programs
promote a person’s sense of worth, together with free and informed
decision making, and appear to have greater impact on teens. A pro-
gram that embraces all aspects of the human person leads to satisfac-
tory outcomes. Teen STAR is such a program. It has resulted in (a)
increased tendency toward abstinence, (b) discontinuation of sexual
activity, and (c) taking personal responsibility for decisions about
when to give oneself to another. An additional factor to be consid-
ered is parental involvement. Our program included three meetings
with parents. A positive correlation between parental involvement
180 Human Fertility: Where Faith & Science Meet
and delay in initiating of sexual activity has been shown (Klaus et
al. 1987). For this reason, we believe that including and integrating
parents is a key factor in the success of the program.
Attitudes precede behavior change; hence, changes in attitude to-
ward primary (decides to abstain from intercourse without having
had it previously) or secondary abstinence (decides to abstain from
intercourse having had it previously) are signiﬁcant. When these
changes settle in, a holistic perception and transformation of life can
be expected. Understanding the following factors helps Teen STAR
foster changes in attitude:
1. e psychological underpinnings of the increased tendency
toward abstinence. Teen STAR’s anthropological rationale en-
courages the free decisions not only by adolescents (our ﬁrst and
foremost goal) but also by anyone who says yes to the program.
e above data show that the values people get in touch with work
both through their innate appeal and through group interaction
(i.e., increased awareness of one’s own dignity and the value of
2. Causes for discontinuation of sexual activity. e participants’
post-test responses appear to show that they stopped activity as a
result of a changed perception of themselves, rather than out of
boredom or peer pressure.
3. Strong personal decisions, reached through internalized un-
derstanding of one’s procreative capacity. e focus on personal
decisions shows the value of the Teen STAR program as a proposal
with a future—with ﬁrm roots. e program is based on convic-
tions and adherence to values.
is study showed a decrease in initiation of sexual activity, along
with an increase in discontinuation of sexual activity. Analysis of the
long-term eﬀects of this type of intervention is important and has
not been done suﬃciently. Preliminary studies indicate that contin-
ued observation and attention to the girls’ fertility patterns reinforces
their decision to remain, or return to, abstinence. e reduction in
pregnancies was sustained in the groups of girls who participated
in the program. However, the goal of long-term follow-up of these
students to assess behavior after high school still needs to be met.
We believe that the eﬀectiveness of the Teen STAR program is
mainly based on certain characteristics that make it substantially dif-
Vigil, Cortés, Klaus Randomized Control Trial of Teen STAR 181
ferent from both abstinence-only and comprehensive sexuality edu-
cation programs. Fertility awareness, coupled with placing a high
value on possessing fertility, in terms of both future procreation and
present understanding of their bodily processes, makes the program
a whole-person experience whose impact may well last for the rest of
participants’ lives. Generally, self-esteem and self-conﬁdence result
from integrating what one understands of oneself into making one’s
own decisions about all behaviors.
For teens, recognizing their fertility not only leads to better knowl-
edge of themselves but also can become a tool for them to recognize
various endocrine-metabolic pathologies. Speciﬁcally, among girls,
certain gynecological problems can be discovered through the chart-
ing of their fertile period by the observation of the diﬀerent pat-
terns of cervical mucus, as well as the regularity of their menstrual
cycles (Vigil et al. 2006a, 2006b). Some disorders, such as polycystic
ovarian syndrome, can be suspected in patients who have noticed
abnormal cervical mucus patterns, as well as an abnormal distribu-
tion of adipose tissue in the body. Symptoms of other pathologies,
such as ovarian and adrenal tumors, problems in the hypothalamo-
hypophyseal-gonadal axis, and autoimmune diseases, could also be
identiﬁed from the cervical mucus patterns, a tool that every woman
should be familiar with (Vigil 2004b). In the case of males, appro-
priate learning of their anatomy and physiology could help them to
discover emerging problems at their juvenile stages, such as obesity,
hypo- and hyperandrogenism, abnormal development of their geni-
tals, growth dysfunctions, and STDs such as Chlamydia trachomatis,
an infection that can impair the fertility of men as well as women
(Vigil et al. 2002b; Gonzales et al. 2004; Vigil and Cortés 2006).
Prompt recognition of abnormalities would hasten medical diagnosis
Today’s challenge for educators is to help young people to perceive
sexuality as a whole, including all dimensions of one’s human ex-
perience. Reason, freedom, and emotions should be integrated into
sex education programs. Programs should overcome the tendency to
separate aﬀections and emotions from bodily requirements, as well.
Personal actions such as precocious sexual activity not only can cause
undesirable consequences, e.g., unintended teen pregnancies and the
182 Human Fertility: Where Faith & Science Meet
contraction of STDs, but also have an impact on the adolescent’s
psyche and emotions.
e Teen STAR program delayed sexual initiation among virgins and
facilitated discontinuation of sexual activity among sexually active
students: program students found more reasons to maintain sexu-
al abstinence than control students (Vigil et al. 2002a; Vigil et al.
2005a). e program was also eﬀective in preventing unintended ad-
olescent pregnancies (Cabezón et al. 2005; Rev. Pan. 2005). Properly
trained high school teachers proved to be eﬃcient in delivering the
program. Teen STAR has shown an impact on pregnancy prevention
that extends for at least the four years of high school when begun
during the ﬁrst year of high school (Cabezón et al. 2005).
We thank Paulina del Río and Professor María Angélica Kaulen
(from the Faculty of Letters, PUC), for their help with the prepara-
tion of the English version of this manuscript. Also, we thank Ana
R. Godoy, BSc (Biochem), for her technical help with the preparation
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