The paper deals with fertility determinants in the populations of immigrants and nonimmigrants in the United States. We consider determinants as follows: age, marital status, education, religion, and race and Hispanic origin. The analyses show that a relation between fertility and place of birth was statistically significant in both populations, women and men. We prove that migration is a major source of variation in fertility between immigrants and non-immigrants, which may lead to the postponement of maternity or marriage. Finally, we find that a duration of residence is positively correlated with fertility among US immigrants
