They said the six-months-pregnant woman was brought to a clinic in a serious condition on December 30 after she complained of pain. She developed some complications, following which she was taken to another hospital, but died en route.
The husband, angered by her death, went to the clinic at around 10.30 pm on January 2 and hacked the female doctor to death while his three accomplices waited outside, police said.
All the four were arrested soon after government and private doctors here staged a protest yesterday, they said.
The Tamil Nadu Government Doctors Association (TNGDA) has announced a state-wide strike today, while the state branch of the Indian Medical Association has called for it tomorrow. Both associations said emergency medical services would not be disrupted.