USAToday:

Teen births are at the lowest ever reported in the USA and both the number of births and birth rate dropped 10% in just one year, according to fresh federal data released today. The number of births to teens ages 15-19 in 2013 was 274,641, which the National Center for Health Statistics says is the lowest since it started tracking such data from all states in 1933. That number is far fewer than in 1970, which was the all-time peak year with 644,708 teen births. The 10% drop in the teen birth rate – to 26.6 births per 1,000 from 29.4 births per 1,000 in 2012—marked another historic low.

Credit goes to increased access to birth control (one of the things conservatives hate about the Affordable Care Act), Plan B (which is a form of birth control), safe and legal abortion (where available), and—yes—teenagers waiting a longer to become sexually active (credit for teens delaying "sexual debut" does not go to abstinence educators, as teens who've had abstinence-only sex ed are less likely to use birth control when they do become sexually active). But our teen pregnancy rate—even at this historic new low—is still pretty embarrassing when compared to the teen pregnancy rates in countries with better sex ed, better health care systems, and easier access to contraception and abortion:

Despite the drastic drops in U.S. teen birth rates, Haub notes that the new low of 26.6 is 5.5 times higher than in Western Europe, where rates are in single digits. The most recent United Nations data shows Switzerland at a low of 1.9 and Luxembourg at a high of 8.3, with most others in the area at 5 or 6 per 1,000 teens.