From the position paper:
Abstinence from sexual intercourse represents a healthy choice for teenagers, as teenagers face considerable risk to their reproductive health from unintended pregnancy and sexually transmitted infections (STIs) including infection with the human immunodeficiency virus (HIV). Remaining abstinent, at least through high school, is strongly supported by parents and even by adolescents themselves. However, few Americans remain abstinent until marriage, many do not or cannot marry, and most initiate sexual intercourse and other sexual behaviors as adolescents. Abstinence as a behavioral goal is not the same as abstinence-only
education programs. Abstinence from sexual intercourse, while theoretically fully protective, often fails to protect against pregnancy and disease in actual practice because abstinence is not maintained.
There's more where that came from. While the journal site provides abstracts of these articles, the full version in only available for a fee. As it happens, we can send a PDF version of the articles via email upon request: tan AT texasaids DOT net.