As the U.S. Latino population in the past decade has surged, many thought immigration was fueling the upswing. However, a higher birth rate among Latinas is the cause, according to a study by the Pew Hispanic Center and reported by the Phoenix New Times.

In particular, one specific group of Latinas is behind the growth: Mexican Americans. Researchers found that between 2000 and 2009, 4.2 million Mexican immigrants came to the United States and 7.2 million Mexican-American babies were born.

In the decade before, there were 4.7 million Mexican-American immigrants and the same number of U.S.-born babies.

Mexican-American immigration (legal and illegal) in the past 10 years has actually declined. However, Mexican-American women are much younger than other women in any minority group. Their median age is 25, an age researchers recognize as healthy for childbearing.

The birth rate in Mexico, conversely, is declining. The national average of seven children in 1960 dropped to just two in 2009.

As a result of the growing number of Latinos in the United States, health care workers will need to focus on diseases and conditions faced by most Latinos, such as diabetes, hepatitis and cardiovascular health. In addition, health information will have to be delivered in the appropriate language and cultural context.