Abstract only| Volume 70, ISSUE 4, SUPPLEMENT , S21-S22, April 01, 2022

# 39. Declines in Pregnancies Among US Adolescents From 2007 to 2017: Behavioral Contributors to the Trend

## Purpose

Pregnancies and births among adolescents in the United States have dramatically declined in recent decades. We aimed to estimate the contribution of three different proximal changes in behaviors to these declines among 14-18-year-olds over the period 2007-2017: delays in age at first sexual intercourse, declines in the frequency of sexual activity, and changes in contraceptive use, particularly the uptake of long-acting reversible contraception (LARC).

## Methods

We adopted an existing mathematical model that predicts number of sex acts per year per adolescent female by age, and the proportion of these that entail use of various types of contraception. We parameterized the model using predicted values from regressions based on six waves of the CDC’s Youth Risk Behavior Survey. We determined mean contraceptive failure rates from the literature. We calibrated our model to reported births using data from the National Vital Statistics System and the Guttmacher Institute. Pregnancy-related costs were calculated using both medical costs for all outcomes and costs to society for adolescent childbearing.

## Sources of Support

This study was funded by the U.S. Centers for Disease Control and Prevention’s National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention [cooperative agreement U38-PS004646]. Additional support was provided by a research infrastructure grant f.