Town and Country police and crews from West County EMS and Protection District responded to the accident on westbound Highway 40 just after 9 a.m. Tuesday.
Four vehicles were involved in the crash right before the Maryville Center Drive exit.
Police said it appears westbound traffic slowed suddenly, probably due to a crash they were already working on the eastbound side of Highway 40. Drivers were unable to stop before striking vehicles in front of them, according to police
Wet roads likely played a role in the accident, authorities confirmed.
Police said there were no serious injuries, but a pregnant woman was taken to the hospital as a precaution.