After a decade of being officially unconcerned by global population growth, the US has taken new initiatives to help cut high fertility rates in developing countries. But here at home, we have some very high fertility rates of our own, particularly among teenagers  ? 6 percent of women and girls in the US between the ages of 15 and 19 give birth each year, a higher rate than in Asia and triple the teen fertility rate in Europe. Jennifer Ludden of member station WBUR in Boston explores the reasons for this, and what makes the difference in communities with low teen birth rates.