The birth rate among American teenage girls has dropped considerably, especially among Hispanics, according to a new report by the Centers for Disease Control and Prevention.

The birth rate among women ages 15-19 decreased by almost half from 1991 to 2011, from 62 to 31 births per 1,000 adolescents.

From 2007 to 2011, the most recent period of the study, the birth rate fell 25 percent, but its decline was even greater among Hispanic girls, who had a 35 percent decrease.

Brady Hamilton, statistician of the CDC's National Center for Health Statistics and coauthor of the report, said that all states except North Dakota and West Virginia reported a drop of at least 15 percent over those four years.

Hispanic teens previously had a much higher birth rate than any other ethnic group - in 2007 it was 21 percent higher than that of African-American girls, while in 2011 it was only 4 percentage points higher.

In the most recent period of the study, birth rates of black adolescents declined by 24 percent, while white teens dropped 20 percent.

Experts attribute the drop to massive warnings in the media about preventing unwanted pregnancies, a growing use of contraceptives in the first sexual relationship, and the use of dual methods of contraception, such as condoms plus the pill. EFE