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 reversible contraception (LARC).

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 496,200, 78,500, and 40,700 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.

中文翻译：

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2007 年至 2017 年美国青少年怀孕率下降：行为因素导致这一趋势

 学习目标

近几十年来，美国青少年怀孕和出生人数急剧下降。我们的目的是估计 2007 年至 2017 年 14 至 18 岁青少年中 3 种近期行为的变化对这些下降的贡献：1) 首次性交年龄延迟，2) 性伴侣数量下降，3) ) 避孕药具使用的变化，特别是长效可逆避孕药 (LARC) 的采用。

 设计

我们采用了现有的迭代动态人口模型，并使用疾病控制和预防中心的青少年风险行为调查的 6 波对其进行参数化。我们将观察到的行为趋势中的怀孕情况与假设十年来行为不变的反事实场景进行了比较。我们按原因、年份和年龄计算结果。

 结果

我们发现，这些行为的改变可以解释这十年间怀孕人数分别减少 496,200 例、78,500 例和 40,700 例，总共节省医疗和社会成本 97.1 亿美元、15.4 亿美元和 7.96 亿美元。 LARC 的采用，尤其是 18 岁青少年的采用，可以在很大程度上解释避孕措施使用的改善。这三个因素并不能完全解释观察到的出生率下降；增加每个伴侣的性行为减少 50% 确实如此。

 结论

尽管所有考虑的行为都会产生重大影响，但首次性交的延迟是这十年来出生率下降的主要原因。与早期模型的差异可能是由于所涵盖的年份和年龄的差异造成的。循证的青少年怀孕预防计划，包括全面的性教育、青少年友好的生殖健康服务以及家长和社区支持，可以继续解决这些驱动因素并减少青少年怀孕。