Jennifer Talbot, 43, was arrested at Ninoy Aquino International Airport in Manila on Wednesday.
A six-day-old boy was reportedly found in her carry-on bag as she attempted to board a plane to the US.
Authorities allege that Ms Talbot did not declare the baby to immigration officials.
The Philippine National Bureau of Investigation (NBI) alleges that Ms Talbot intended to “conceal and sneak the baby out”.
The baby’s mother and father have been charged under a child protection law, authorities said. The boy has been placed in the custody of social services.
Ms Talbot, from Ohio, was not able to provide a boarding pass or any documentation for the baby, the agency said.
Wearing an orange shirt and in handcuffs, Ms Talbot attended a news conference on Thursday, when the charges against her were announced. She made no comment.
If found guilty, she could face life in prison, Manuel Dimaano, head of the NBI’s airport division, told reporters.
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US Embassy officials have been informed of Ms Talbot’s arrest, the Associated Press reported.
Following her arrest, Ms Talbot did present a document which she claimed gave her consent to take the baby to the US, the NBI said.
But the document was not signed by the baby’s mother, the agency said.