Declines in Pregnancies among US Adolescents from 2007 to 2017: Behavioral Contributors to the Trend

Study Objectives: Adolescent pregnancies and births in the United States have undergone dramatic declines in recent decades. We aimed to estimate the contribution of changes in 3 proximal behaviors to these declines among 14- to 18-year-olds for 2007-2017: 1) delays in age at first sexual intercourse, 2) declines in number of sexual partners, and 3) changes in contraceptive use, particularly uptake of long-acting Design: We adapted an existing iterative dynamic population model and parameterized it using 6 waves of the Centers for Disease Control and Prevention's Youth Risk Behavior Survey. We compared pregnancies from observed behavioral trends with counterfactual scenarios that assumed constant behaviors over the decade. We calculated outcomes by cause, year, and age. Results: We found that changes in these behaviors could explain pregnancy reductions of 496,20 0, 78,50 0, and 40,70 0 over the decade, respectively, with total medical and societal cost savings of $9.71 billion, $1.54 billion, and $796 million. LARC adoption, particularly among 18-year-olds, could explain much of the improvement from contraception use. The 3 factors together did not fully explain observed birth declines; adding a 50% decline in sex acts per partner did. Conclusions: Delays in first sexual intercourse contributed the most to declining births over this decade, although all behaviors considered had major effects. Differences from earlier models could result from differences in years and ages covered. Evidence-based teen pregnancy prevention programs, including comprehensive sex education, youth-friendly reproductive health services, and parental and community support, can continue to address these drivers and reduce teen pregnancy.

Automated summary

The study found that there has been a significant decline in adolescent pregnancies and births in the past decade in the United States. The delay in first sexual intercourse, reduction in the number of sexual partners, and changes in contraceptive use, especially the adoption of long-acting methods, were identified as major contributors to this decline. However, these factors alone did not fully explain the observed decrease in birth rates; a decline in the frequency of sexual acts per partner was also necessary. The findings highlight the importance of evidence-based teen pregnancy prevention programs and comprehensive sex education in addressing these factors and reducing teen pregnancy.