Santorum's campaign said Friday that 3-year-old Bella had been returned to the hospital. She has the rare genetic condition Trisomy 18 and was hospitalized earlier this year with pneumonia.
Santorum's campaign did not identify the hospital or say why her parents took Bella there.
The former Pennsylvania senator is spending a few days off the trail for Easter.
Bella's condition typically proves fatal. Santorum often says she wasn't expected to live past her first birthday.