The incident took place in the Mhasrul locality where victim Suvarna Gaikwad was being harassed mentally and physically for dowry since her marriage to Khanderao Gaikwad in June last year, they said.
The young woman was being tortured to bring a dowry of Rs 1.5 lakh for building a house.
Later, when her in-laws came to know that she was pregnant, they took her to a 'godman' Shyambaba Shinde at Niphad, who told them that she was carrying a girl, police said.
Suvarna was told to abort the girl child but when she refused to do so, she was allegedly roughed up by her husband, and family, including the mother-in-law killing the foetus on April 4.
The matter was brought to light by Mahendra Datrange, President of Nashik unit of Blindfaith Eradicating organisation following which the husband, his brother Vijay Gaikwad, maternal father-in-law Dilip Suryavanshi and one of his kins Jalinder Suryavanshi was arrested yesterday, police said.
Offences have been registered against them under different sections of IPC at panchavati police station yesterday, police said.
Suvarna's family, which alleged murder of the child, is demanding the arrest of her mother-in-law Bibabai, Shinde and others involved in the killing.