According to the complaint filed by the 23-year-old woman's mother-in-law, the accused allegedly beat her child to death on August 2 with the help of her stepfather, with whom she was having an extra-marital affair, said Inspector Rajan H Sasthe of Bhiwandi police.
The woman was arrested late last night from the Bhiwandi area here, he added.
Complainant Irfana Mohamad Aslam Ansari has claimed that her daughter-in-law, Firdous Khuyyam Ansari, was having an illicit affair with her stepfather Rashid Janmohammad Ansari (35). She has alleged that the child was a hindrance in their relationship, so the duo killed the baby, Sasthe said.