Sardella delivered the boy at her parents' house on New Year's Day 2007 while she was home on break from her freshman year at Drexel University. Her mother, Stephanie Leone, found the body Jan. 22 in a duffel bag in the trunk of her car. Sardella later told family member she did not feel a heartbeat and presumed the newborn had died.
Authorities have said the baby died of asphyxiation about a minute after Sardella gave birth.
Sardella is the granddaughter of Albert Piscopo, the chief executive of the Glenmede Trust Co. investment firm.
She left the courthouse with family members after the brief plea hearing and remains on electronic home monitoring. Her sentencing was set for Jan. 22 - two years to the day after the decaying corpse was found.
Delaware County Judge Patricia Jenkins did not lift a gag order issued earlier in the case, and Deputy District Attorney Michael Galantino and defense lawyer Arthur Donato did not comment afterward. Donato previously said his client suffered from "denial-of-pregnancy syndrome."
Sardella also pleaded no contest Tuesday to abuse of a corpse and concealing the death of a child. A third-degree murder count was dismissed.