The accused, identified as Bagesh (18), a resident of Shahjanpur in Uttar Pradesh, raped the one-and-a half-year-old baby girl yesterday when her mother had gone outside for some work, they said.
Later, the victim was taken to a nearby hospital, but in view of her serious condition, she has been referred to a district hospital for surgery.
The accused has been arrested while the further probes are on, police added.