The 15-year-old delivered the baby on May 5 on the night of her marriage to Shahid, a deaf and mute boy, after complaining of stomach cramps.
Following the incident, a meeting of a community panchayat was sought by the family members that decided that the couple should be separated.
SP (Rural) Vijay Gautam said they have received a complaint from the girl who is an orphan.
"The victim has accused her brother-in-law Anwar of sexually exploiting her for years which made her pregnant. The police are investigating the matter and will quiz Anwar," he said.