A 21-year-old woman has been booked by police on a complaint by her teenage nephew alleging sexual assault by her over a period of time.

The 15-year-old boy, accompanied by his grandfather, lodged the complaint against his aunt in the All-Woman Police Station at Mayiladuthurai near here, police said.

Police registered a case against the woman, cousin sister of the boy's father, under the Protection of Children from Sexual Offences Act.

According to the complaint, the woman lured the boy studying in class X and had sex with him frequently and in the process became pregnant. She gave birth to a baby girl at a hospital in Thirukadaiyur near here on December 8, it said.

The boy was living with his grandfather as his parents were separated.

Of late, she was pestering the boy's grandfather to get her married to the boy and unable to bear it, they gave the police complaint yesterday.