过去二十年的特点是在内部移民执法和提高的压力空前增加，由于无证移民的家庭分离和收入损失的担忧。Using vital statistics on infant births from the National Center of Health Statistics for the 2003 through 2016 period and a difference-in-differences design, we compare the health outcomes of infants with likely undocumented mothers before and after the intensification of immigration enforcement within U.S. counties. We find that intensified enforcement, especially during the third trimester, increases the likelihood of low birth weight (<2500 grams). We also present suggestive evidence that the effect could be driven by heightened stress and fears associated to police-based enforcement during pregnancy. The findings underscore the importance of current immigration policies in shaping the birth outcomes of many American children.