"It's true, I killed them, and I will regret it for the rest of my life," the diminutive Hui Zhang, 34, said at the start of the hearing.
Hui said she merely acted in self-defence as the furious parents of the dead newborn attacked her and her boyfriend with a butcher's knife.
Her boyfriend and co-accused Te Lu, also 34, denied helping Hui kill the couple.
"I was sucked into a whirlwind of nightmares but I am innocent," he told the court.
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Several days later, a guide dog found a human torso in the same area, but the hunt for further remains was fruitless.
Police knew the victims were Asian and initially thought the murders could be the work of the Chinese mafia, or of Luka Rocco Magnotta, a Canadian convicted of killing and dismembering a Chinese student who spent time in Paris.
But before the bodies could even be identified, Hui and Te turned themselves in.
She and her partner decided to offer the child's parents money to try to get them not to report the boy's death.
They invited the parents to their home, but said their plans quickly went awry faced with the fury of the grieving couple.