The young mother, who gave birth to her first child three months ago, was frustrated and angry at herself for not having a son, SSP Akash Tomar said.
In a fit of rage, Aarti smothered the infant with a pillow on Sunday and stuffed the body in a washing machine, police said.
Though the accused initially claimed that the child had been kidnapped, she later confessed to her crime, Tomar said.
The family members of the woman claimed that they had never pressurised her for a boy, police said.
The case is being investigated, they added.