"A seven-month pregnant woman was arrested and 21.734 kg opium has been seized from her custody at her residence in city's Sethiyanagar area," sub-inspector M N Saikh said.
The woman, identified as Shushila Jimmy Mcwan (40), was first taken to Valsad civil hospital and was arrested after undergoing all necessary tests, Saikh said.
She has been charged with offences under Narcotic Drugs Psychotropic Substance Act, he said.
Police raided the house based on specific tip-offs and seized a huge stock of the narcotic substance, he said.
Two more men were also present at the house, but they managed to flee, Saikh added.
According to primary investigation, the woman had connections with a Mumbai-based drug dealer, known as Shetty, for whom she worked, police said.