Hispanic women have been part of that trend, possibly due to the economy and to illegal immigration crackdowns in some states that reduce the number of young Hispanic females entering the country from Mexico and other nations, said John Santelli, a Columbia University professor of population and family health.

That means new immigrants are having less impact on birth statistics, and second- and third-generation families are having more influence.

As time goes on, Hispanics — like other immigrant groups before them — tend to adopt American customs and practices.

“There is more attention on education, career, and the future,” said Dr. Janet Realini, head of Healthy Futures of Texas, a San Antonio-based organization focused on preventing teen and unplanned pregnancies.