As I pointed out in 2002: The last illegal alien amnesty had unexpected repercussions that echoed for years in California. It turns out that the 1986 amnesty for illegals set off a big baby boom among its beneficiaries—inevitably worsening the subsequent crowding in schools and emergency rooms, not to mention burgeoning votes for Democrats.

Demographers Laura E. Hill and Hans P. Johnson of the Public Policy Institute of California wrote in "Understanding the Future of Californians' Fertility: The Role of Immigrants:"

"Between 1987 and 1991, total fertility rates for foreign-born Hispanics [in California] increased from 3.2 to 4.4 [expected babies per woman over her lifetime]. This dramatic rise was the primary force behind the overall increase in the state's total fertility rate during this period. Were it not for the large increase in fertility among Hispanic immigrants, fertility rates in California would have increased very little between 1987 and 1991. 

"Why did total fertility rates increase so dramatically for Hispanic immigrants? First, the composition of the Hispanic immigrant population in California changed as a result of the Immigration Reform and Control Act (IRCA) of 1986. In California alone, 1.6 million unauthorized immigrants applied for amnesty (legal immigrant status) under this act. The vast majority were young men, and many were agricultural workers who settled permanently in the United States. 

Previous research indicates that many of those granted amnesty were joined later by spouses and relatives in the United States... As a result, many young adult Hispanic women came to California during the late 1980s. We also know that unauthorized immigrants tend to have less education than other immigrants and that they are more likely to come from rural areas. Both characteristics are associated with high levels of fertility. As a result, changes in the composition of the Hispanic immigration population probably increased fertility rates. 

"Another possible reason for the sudden increase in fertility rates for Hispanic immigrants is also related to IRCA. Because many of those granted amnesty and their spouses had been apart for some time, their reunion in California prompted a "catch-up" effect in the timing of births..."