The collision happened just after 3:30 p.m. on Friday, Delta Police said.
Sgt. Sarah Swallow said a police officer was responding to an assault call and travelling north on Scott Road through 80th Avenue, when a vehicle turned left in front of him, causing the vehicles to collide.
"There did not appear to be any visible injuries at scene," Swallow said. "However the pregnant woman and three-year-old in the other car were transported to hospital for precautionary measures."
The officer was also transported to hospital and released.
As a police officer was involved, Delta Police contacted the Independent Investigations Office, but the agency declined to investigate as it did not meet its investigative requirements.