Final answer:
Factors contributing to the decline in the teenage pregnancy rate in the U.S. include increased use of contraception, delayed initiation of sexual activity, and higher education levels among teenagers. Decreased access to reproductive healthcare does not contribute to the decline.
Step-by-step explanation:
The factors contributing to the decline in the teenage pregnancy rate in the U.S. include increased use of contraception, delayed initiation of sexual activity, and higher education levels among teenagers. However, one factor that does not contribute to the decline in teenage pregnancy rate is decreased access to reproductive healthcare.