With the federal government having long treated birthright citizenship as a requirement of Section 1 of the 14th Amendment, President Trump’s executive order denying it to children of noncitizen, non-permanent resident mothers faces an uphill court battle. Still, opponents of birthright citizenship can hope that the result will elucidate Section 1’s much-debated “subject to the jurisdiction thereof” phrase and clarify whether an amendment is necessary to reinterpret it.

This issue is not trivial. My colleagues and I at the Center for Immigration Studies recently put together a preliminary estimate that illegal immigrant mothers gave birth to between 225,000 and 250,000 babies in 2023. That number is larger than the total number of births in any single state in 2023 except Texas and California. All of these children are automatically U.S. citizens, and through their birth they increase their parents’ chances of remaining in the country as well.

With the U.S.’s sub-replacement level fertility, isn’t having more children exactly what our country needs? “I want more babies in the United States of America,” Vice President J.D. Vance recently declared, and with good reason. Deaths will soon outnumber births in the U.S., bringing the risk of economic and cultural stagnation as our population ages.

Why not embrace so-called “anchor babies” as well as legal immigrants who boost the nation’s fertility rate? Put another way, if having children is increasingly a “job that Americans won’t do,” why not bring in people who will?

A low national fertility rate is indeed a problem—but immigration is not the solution. First, immigrant fertility is only slightly higher than native fertility. A standard measure called the total fertility rate (TFR) makes that clear. TFR is the number of children that women would have in their lifetimes if their rates of childbearing at each age matches today’s rates. In 2023, native-born Americans had a TFR of 1.73. Averaging in the immigrant rate of 2.19 raises the national TFR to only 1.80—still well short of replacement level.

Because their fertility is already low, immigrants have only a tiny effect on the national TFR despite constituting a record share of the U.S. population. In fact, doubling immigration would still raise the national TFR to only 1.87. To boost the TFR through immigration, we would need to recruit from the few places where fertility is still high: mainly sub-Saharan Africa and the Middle East. Needless to say, the difficulty of integrating such culturally different peoples likely outweighs the fertility benefit.

A second reason that immigration is not the solution to low fertility is that it can actually discourage some natives from having children. In a new report, I review the academic literature showing that the depressive effect of immigration on native fertility likely eliminates the small gain from the higher immigrant TFR.

There are multiple reasons why that is the case. The entry of immigrants into a labor market puts downward pressure on wages and employment opportunities, creating an uncertain economic environment that discourages natives in the affected industries from having children. Immigration also increases demand for housing, driving up the price for first-time homebuyers who desire more living space before they start a family. On a cultural level, immigration adds to the ethnic diversity of a community, which scholars such as Robert Putnam have found decreases social trust. With less community engagement comes fewer opportunities for marriage and childbearing.

Immigration can encourage fertility in some ways, such as lowering child care costs—but the net effect appears to be negative. Furthermore, working-class Americans are hardest hit. They face greater competition from immigrant labor; they are more likely to be renters or first-time homebuyers; and they rely more on traditional social networks characteristic of close-knit communities. My colleague Mark Krikorian likes to say that immigration is not so much a “left-right” issue as it is “up-down,” meaning its negative consequences tend to affect Americans who are already struggling.

Raising the national TFR enough for Americans to replace themselves requires a multi-pronged strategy. Experts have suggested building more low-density housing, offering subsidies to married couples to have additional children, rolling back educational “degree inflation” that requires young people to delay career and family formation, and fostering a culture that values children as a crucial part of a community. In adopting these strategies to increase native fertility, policymakers should not ignore the important role that immigration restriction can also play.