Over 2005-2019, the number of neonatal intensive care units (NICUs) grew by 10%, and the number of NICU beds increased by 30%. This expansion in intensive care has raised concerns over unwarranted intensive care admissions. In this study, we examine whether the greater supply of NICUs causally raises admission rates. Our event-study results show that an additional NICU opening in a county raises the share of newborns admitted to the NICU by 8%. The majority of new NICU admissions come from healthier newborns (2,500 grams and over) rather than very premature newborns (<
1,500 grams). Admission for the smallest newborns (those under 1,500 grams) only increases in counties with limited NICU access. In these areas, greater NICU supply also reduces mortality, but only for very small newborns (<
1,500 grams). Together, our findings suggest a tradeoff, where higher NICU supply reduces neonatal mortality for the most vulnerable infants while also raising admission for healthier newborns.