Study Enrollment

The Contraceptive CHOICE Project was a prospective cohort study involving 9256 St. Louis area girls and women 14 to 45 years of age, in which the use of LARC methods was promoted to reduce unintended pregnancy.16 Participants were recruited through referral from medical providers, word of mouth, and study flyers. The Washington University School of Medicine in St. Louis Human Research Protection Office approved the study protocol before recruitment began, and all participants provided written informed consent. Participants 14 to 17 years of age provided written assent, and a parent or guardian provided written consent. Minors could enroll under a waiver of parental consent if they did not know the whereabouts of their parents or guardians or if they did not want their parents or guardians to know that they were seeking contraception. We enrolled four minors using the waiver.

Women and adolescent girls were eligible to participate in CHOICE if they were English-speaking or Spanish-speaking, resided in the St. Louis region or sought contraceptive services in selected community clinics, had no desire for pregnancy for at least 12 months, were sexually active or planning to be sexually active with a male partner during the next 6 months, and were not using a contraceptive method or were willing to switch to a new, reversible contraceptive method. Women and adolescent girls were ineligible if they had undergone a hysterectomy or sterilization procedure.

Study Design

CHOICE provided standardized contraceptive counseling to study participants regarding commonly used reversible contraceptive methods.17 Methods were presented in order from most to least effective, and the potential side effects, risks, and benefits of each method were reviewed. Participants were provided with their chosen method at their enrollment session in accordance with evidence-based clinical guidelines.18,19 If medical contraindications did not allow for same-day insertion of a LARC device (e.g., if pregnancy could not be ruled out definitively or if the participant had active cervicitis), participants received a shorter-acting method, such as oral contraceptive pills or depot medroxyprogesterone acetate (DMPA) injection, until their chosen method could be initiated. During the enrollment session, study staff performed a baseline interview, and participants were screened for sexually transmitted infections.

Participants were followed for 2 to 3 years, depending on their enrollment date. Telephone interviews were administered by study staff at 3 and 6 months and every 6 months thereafter. Participants received a $10 gift card after every completed follow-up survey. During the baseline and follow-up surveys, we collected detailed information regarding demographic characteristics and reproductive history, including contraceptive method use and satisfaction, sexual behavior, and pregnancy.

This analysis involves the 1404 adolescents who enrolled in CHOICE between 14 and 19 years of age, from 2007 through 2011; 716 teens were followed for 3 years, and 688 teens were followed for 2 years. At each follow-up survey, we asked participants if they had had a pregnancy. Participants who contacted study staff outside a scheduled survey or came to the clinic with concerns about possible pregnancy completed a urine pregnancy test. We recorded all pregnancies in a pregnancy log and documented the contraceptive method used at the time of conception. If the outcome of the pregnancy was known at the time of the survey (e.g., birth, miscarriage, or abortion), it was documented in the pregnancy log. If a participant was currently pregnant, we subsequently contacted her to record the pregnancy outcome.

Study Outcomes

The primary outcomes of the study were the rates of pregnancy, live birth, and induced abortion observed among participants who were 15 to 19 years of age at any time during study participation. We compared the rates in the CHOICE cohort with the most recent available rates among all U.S. teens 15 to 19 years of age, from 2010,1 and hypothesized that the rates in CHOICE would be lower than the national rates. Because the U.S. rates represent all teenage girls and women 15 to 19 years of age, including those who are and those who are not sexually experienced, we also compared the CHOICE rates with the national rates reported among sexually experienced teenage girls and women in 2008 (the most recent available data).20 In addition, we examined rates according to age and race as secondary outcomes. All analyses of rates of pregnancy, live birth, and induced abortion; teen-years of use of contraceptive methods; and failure rates of contraceptive methods included data collected when members of the cohort were 15 to 19 years of age.

Statistical Analysis

We used frequencies, percentages, medians, and ranges to describe the demographic and reproductive characteristics of the participants at the time of study enrollment. A chi-square test was performed for categorical data, and a Wilcoxon two-sample test was performed for continuous data that was not normally distributed.

For this analysis, we calculated annual means and 95% confidence intervals for rates of pregnancy, live birth, and induced abortion from 2008 through 2013, because the number of pregnancies and pregnancy outcomes that occurred among teenage CHOICE participants each year was small. Each rate represents the total number of events (i.e., pregnancy, birth, or abortion) that occurred among the participants divided by the total amount of time contributed from 2008 through 2013. For a pregnancy to be considered in the analysis, the outcome of the pregnancy (i.e., birth or abortion, for the purposes of this study) had to occur before 20 years of age. This is the same approach used by the National Center for Health Statistics in calculating U.S. rates.1 We calculated the time contributed by each participant during which she was not pregnant. If at the last survey the participant reported she had not been pregnant since the previous contact, we subtracted 6 weeks of contributed time to account for the possibility of an early-stage and unknown pregnancy. For a participant who had a pregnancy, we subtracted the total time she was pregnant plus 1 month if she delivered, to account for postpartum infecundity. For participants who were lost to follow-up, the last date of contact was the cutoff point for outcomes and contributed time. All analyses were performed with the use of Stata software, version 11 (StataCorp).