The body was found at a pool in the Upazila’s Putkhali Union on Saturday morning.
Police are yet to identify the woman, who appeared to be in her mid-20s.
Morelganj police OC Md Aslam Khan said locals informed police after seeing a body floating in the pool beside the road.
After police retrieved the woman’s body, it was sent to Bagerhat Sadar Hospital for autopsy.
The woman, wearing a black burka, was at least six months pregnant. No one in the area could recognize her, said OC Aslam Khan.
A case has been filed at Morelganj Police Station over the incident.