"Kids are no longer overrunning us. It changes the priorities for the state," demographer Dowell Myers said.
The number of California births has been declining since 2007, state public health records say, the statewide fertility rate slipping to 1.94 children per woman.
A rate of 2.1 children per lifetime is regarded as a rate that replaces population, the San Jose Mercury-News said.
Changing behaviors and economic trends are driving down the number of babies born, state demographer Walter Schwarm said, but no single cause easily explains the trend. He added the uncertainty of the recession delayed births, as did women's economic gains that raise the cost of staying out of work.
Birth rates around the world are falling. Births among all women of childbearing age have dropped by 8 percent since 2007, the Pew Research Center said.
"There's less children to compete with" for schools and later jobs, said Carlin Graveline, 30, of San Jose, who had her second child in August and claims to be the youngest mom she knows of in her neighborhood, but "it's going to be a heavy load on their shoulders for a smaller population to be taking care of an older population."