The factors most strongly related to the decline in teen pregnancies and teen births from 1991 to 1995 were an increase in abstinence and a decline in the percentage of teens who were married. Increased abstinence among teens accounted for most of the reduction in births and for 67 percent of the reduction in out-of-wedlock teenage pregnancies.
Source:
"An Analysis of the Causes of the Decline in Non-marital Birth and Pregnancy Rates for Teens from 1991 to 1995"
Mohn, Joanna K.
Tingle, Lynne R., and Finger, Reginald
Adolescent and Family Health Vol. 3, Number 1. , 2003. Page(s) 39-47.
(HT: FamilyFacts.org)

Married teens were factored into "teen pregnancies"? Why?
From http://www.guttmacher.org/media/nr/2004/02/19/index.html
“An analysis by researchers at The Alan Guttmacher Institute found that about 25% of the decline in teenage pregnancy between 1988 and 1995 was due to decreased sexual activity, while 75% was due to more effective contraceptive practice. This analysis utilized sexual behavior data from the 1995 National Survey of Family Growth (NSFG). The next NSFG has not yet been completed.”
And from http://www.guttmacher.org/pubs/2006/09/12/USTPstats.pdf
The highest rates of non-Hispanic white teenage pregnancy are in the Bible Belt: Arkansas, Alabama, Georgia, Kentucky, Mississippi, South Carolina and Tennessee.
The lowest rates are in: Minnesota, New Jersey, North Dakota and Wisconsin.
One of the authors has a vested political interest in abstinence; he's one of the people that opposed the HPV vaccine on the grounds that it would remove God's punishment for the sexually active. As we'd say in the audit business, professional skepticism should be heightened w/re/to the article.