The Sûreté du Québec says he is considered a witness at this point in the investigation.
Cheryl Bau-Tremblay, 28, was reported missing earlier this week after police said she left her home on foot and didn't return.
Bau-Tremblay is five months pregnant.
Police said she had returned home from a few days in the Eastern Townships just before she disappeared.
The Sûreté du Québec is now assisting the Richelieu-Saint-Laurent with the investigation.
Bau-Tremblay has still not been found. She is described as five-feet-two-inches tall, about 140 lbs with black hair and blue eyes. She speaks French and has a tattoo on her wrist.
Anyone with information is asked to call Info Crime at 450-922-7001 ext. 399.