A pregnant woman in Nalla Sopara locality in Palghar was arrested for allegedly killing her mother-in -law, police said on Saturday.

The incident took place on Friday when four-month pregnant Chandni Patwa (25) allegedly attacked her mother-in- law Urmila (56) with a knife at their residence in Nalla Sopara East over a heated argument, an official at Nalla Sopara police station said.